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Class              Q  i:iB.ti        u ,  1 
BookT>44-^^^^^^^^'^  Vol  

GIVEN  BY 


PtSTERSOIir  s 


FAMILIAR  SCIENCE; 

OR  THE 

SCIENTIFIC  EXPLANATIOU 

OB 

COMMON  THINGS. 

E»ITED  BY 

R;  Peterson, 


HIMBKB  OF  THS  ACADEMY  OF  NATUEAL  SCIENCES,  PHIL ASZLPHIA. 


L'homnie,  sur  un  monde  de  poussiere  qui  tourn6  ct  Pemporte  avee 
rapidite,  a  mesure  I'immensite  des  cieux.  II  vous  dira  la  grandeur  det 
antres,  leur  vitesse  et  leur  distance;  interrogez-le  sar  I'atume  qui  eat 
(lepras  de  lui,  il  gardera  le  silence. 

X.  Aim'c  Martin. 


ONE  and  tenth  thousand. 

J^HILABELPHM : 

J.  B.  LIPPING  OTT  &  GO, 


\ 


Office  of  tiik  Cor^TROLLEEs  of  Pi3  blic  Schools,  j 

First  School  District  of  Pennsylvania,.  \ 
Philad'a.,  Sept.  11,  1S51. 
At  a  Meeting  of  the  Controllers  of  Public  Schools,  First  D.'stricl 
af  Pennsylvania,  held  at  the  Controllers'  Oltice,  Tuesday,  Sept  9» 
ISfjl,  HiC  loilowing  resolution  was  adopied. 

Resolved,  Tbat  the  work  entitled  Familiar  Science,"  be  intro- 
duced into  the  Grammar  Schools  of  this  Di>lrict. 

Ho  BERT  J  Hemphill,  Sec'ry. 


At  a  Tneetin«:  of  the  Board  of  Education  of  the  Brooklyn  Public  Schools 
held  Dec.  2,  1851,  the  following  resolution  was  adopted  ; 

Hesolvedy  Thai  "  Peterson's  Familiar  Science,"  be  adopted  as  a  text 
Dook  for  use  in  the  rublic  Schools, 

W.  S.  DILLINGHAlVf, 
Chairman  of  Com.  on  School  Booki 
Ittest,  8.  L.  HoLMM,  Sec'y. 

Elntered  according  to  the  Act  of  Congress,  in  the  year  185L  by 

ROBERT  E.  PETERSON, 
In  tlie  Clork'fl  OHice  of  the  District  Court  of  the  Eastern  DidtriCI 
of  PtJiLcsyi  vania. 


0 


'  -  '  '  •  ^  '  jr^,  -?*     V  r"« 

A  part  of  ijie  followml^  woflr' i^'"from  the  pen  0/  the  Rev. 
i)r.  Brewer,  of 'I'wjaityjiall,  lilso,  TIe&d  Musi  en 

of  King's  Colleg6^^iSuihMri|fti^WQh-^^  liiiioii  with  iying's 
College,  London.  It ■  oonfemairTmiciT-Tiscfulv  as  well  as  prac 
ti(  al  scieuuiic  knowledge,  in  a  very  popular  and  entcrtainiiig 
ferm , 

The  work,  however,  as  it  emanated  from  the  English  press, 
was  not  only  in  many  points  unsuited  to  the  American  pupil, 
but  was  OAcreniely  deficient  in  its  arrangement.  The  Editor 
has  endeavored  to  remedy  these  defects,  by  making  many 
additions,  as  well  as  by  altering  those  parts  which  were 
purely  applicable  to  Great  Britain,  and  adapting  the  whole 
to  our  own  countiy.  As  to  the  arrangemcnl,  he  feels  con- 
fident it  will  be  the  means  of  facilitating  the  acquirement  of 
the  great  amount  of  useful  information  embodied  in  the  work, 
and  also  of  classifying  in  the  mind  of  the  pupil  the  different 
branches  of  which  it  treats. 

"  No  science  is  more  generally  interesting  than  that  which 
3xplains  the  common  phenon^ena  of  life.  -  We  see  that  salt 
And  snow  are  both  wliite,  a  rose  red,  leaves  green,  and  the 
nolet  a  deep  purple ;  bul  how  few  persons  ever  ask  the  rea- 
son why  !  We  know  that  a  flute  produces  a  musical  sound, 
and  a  cracked  bell  a  discordant  one — that  tire  is  hot,  ice  cold, 
and  a  candle  luminous — that  water  boils  when  subjected  to 
heat,  and  freezes  from  cold ;  but  when  a  child  looks  up  into 
our  face  and  ask  us  'why' — how  many  times  is  it  silenced 
with  a  frown,  or  'called  very  foolish  for  asking  such  silly 
questions  !' 

This  book,  intended  for  the  use  of  families  and  school's, 
explains  about  two  thousand  of  these  questions,  and  is  writ- 
ten in  language  so  plain  as  to  be  understood  by  all.  Care 
has  been  taken,  however,  in  the  endeavor,  to  render  it  intelli- 
gible to  the  young,  to  avoid  that  childish  simplicity  which 
might  he  unacceptable  to  those  of  riper  years. 

A  very  full  Index  is  appended  to  the  work,  to  facilitate  tha 
pupil's  researches. 


f  Dr  Srewer'fl  Frefacct 

iii 


1^627 


PREFACE. 


In  the  Preface,  to  the  English  edition,  already  mentioned, 
there  is  an  aneodote  related,  which  is  so  appropriate,  that  it 
IS  here  given  in  full. 

remarkable  instance  came  before  the  author  a  few 
months  since,  of  the  statement  made  in  the  earl}  part  of  this 
Profacc.  The  conversation  was  about  smoke — why  it  waa 
black,  and  not  white  like  the  fine  dust  of  lime.  A  Httle  child 
who  was  present,  asked,  *  Why  is  the  kettle  so  black  with 
smoke?'  Her  papa  answered,  *  Because  it  has  been  on  the 
fire.'  *  But,'  (urged  the  child)  '  what  is  the  good  of  its  being 
black  V  The  gentleman  replied,  '  Silly  child— you  ask  very 
foolish  questions — sit  down  and  hold  your  tongue.'  " 

Information  of  that  description  is  just  what  children  love 
to  gain,  and  what  many  older  persons,  who  are  even  tolera- 
bly well  informed,  are  not  competent  to  give. 

The  Editor  trusts  his  book  may  prove  an  interesting  and 
useful  companion  to  both  old  and  young,  either  in  the  family 
circle,  or  in  the  school-room.  / 

Twenty-five  thousand  copies  of  the  English  edition  of  the 
above  work  were  sold  in  London  in  less  than  two  years. 

Philadelphia,  Apkil,  1851. 


The  following  is  extracted  from  a  letter  received  by  th« 
Editor,  from  the  Hev.  Dr.  Brewer : 

Robert  E.  Peterson,  Esq. 

Dear  Sir — I  have  received  the  American  edition  of  my 
Guide  to  Familiar  Science,  and  thinlr  it  very  handsomely 
printed  and  skilfully  rearranged.  I  shall  esteem  it  an  honor 
to>*give  my  full  consent  to  your  expressing  my  approbation 
of  your  edition  of  my  Familiar  Science,  and  I  thank  you  foi 
fche  k^idness  in  having  sent  me  a  copy. 

Dear  Sir, 

Yours  truly, 

E.  0.  BREWER. 

St  Helen,  Isle  op  Jersey, 
3d  Dec.  1851. 


CONTENTS. 


PART  I.— HEAT. 

UIB. 

CiiAP  I  -TheSttn.   7 

Sec.  1.  The  sun  the  primary  source  of  heat.      ,        -  7 

2.  Caloric.       .          .          .         ,                   ■  8 

II. — Electricity.       ....         -  9 

Sec.  1.  Electricity  produced  by  friction.            .         .  9 

2.  Lighlmiii!:.             .          .          -         *         c  13 
§  1.  Dano-er  from  licfhTning.       ,         ,  19 

2.  Lij^tiMiinsx  conductors.         •         .  28 

3.  Ettecis  of  lightning.           ...  33 

3.  Thund-r.     ......  33 

<^  III.— -Chemical  Action.         .         •         •         .         c  43 

Sec.  1   Expansion.            .          .          .          »          ,  43 

§  1.  Exjiansinn  of  liquids  and  gases.     ,         .  43 

2.  l']yMa[ifiir)n  of  metals.          •          .          .  54 

3.  Venrilanon.    .          ,         .          ,         ,  60 

2.  Cotidiu'iion  oi  heat.          ....  79 
^  1.  Conductors  of  heat.            •         .  79 

2.  Convection.    .         •         •         •         .  99 

3.  Change  of  state.     .          .          .          •          .  107 
§  1.  Latent  heat.             •         •          •          ,  110 

2.  Ehullition.     .          ,                    ,          ,  113 

3.  Evaporation.           •         .         ,         ,  121 

4.  Vaporization.           •         «          •          ,  131 

5.  Liquefaction.           •         •         •         •  1.35 

4.  RndialKMi.  137 

5.  Reflection.             .         •         •         •         .  144 

6.  Absorption.            •          •          .          •          •  149 
IV. — ^Mechanical  Action.     •         •         •         ,  ,101 

Sec.  1.  Percussion.            .          .          •         •          ,  181 

2.  Friction.      ......  1G5 

3  Condensation  or  compreision.     •         .         ,  188 

PART  II.— NON-METALLIC  ELEMENTS. 

HHAP  I.— Oxygen  and  Oxides.     .         .         .        •        ,  17« 

Sec.  1.  Oxvjjen.      ......  170 

2.  Oxides   175 

**      II. — Hydrogen  and  Wateb.           •         «         >         •  184 

Sec.  1.  Hydrogen.             .         •         •          *  184 

2.  Writer   187 

"    III. — Nitrogen  and  Air.       .         •         •         •         •  192 
Sec.  I.  Nitrogen.    .         ,         •         •         •  ,192 

2.  Air.   193 

«     rV.— Carbon.  195 
5ec.  1.  Carbonic  acid.       .         .         .         ,  .200 

§.  Effervescence.         •         •         •         t  216 
2-  Carburetted  Hydrogen,     .         •         .  .229 


VI 


coNTEii  rs. 


CRAP.  V  -PHospnorviJs  and  Phosphueettei»  Htdrogen.  223 

Sec.  1.  Phosphorus.          .....  223 

2.  Phosphurctted  hydrogen.            .         ,         ,  22(5 

VI.— Combustion.       ......  2*^ 

Bee.  1.  Sponlaneous  combustion.            .         .         «  249 

2.  Flame.       .         .         >         o        .        .  250 

PART  III.— METALS. 

CHAP.  J  —Metals  and  Allots.    .....  269 

Sec.  1.  Metuls   239 

2.  AUf^ys.        .          .         •          .          .  264 

'•*     11. — Glass,  Pokcelain,  and  Earthenware.       .        ,  266 

PART  IV.— ORGANIC  CHEMISTRY 

CHAP.  T.— Sugar   .274 

"     II , — Fekmentation  and  Put  refaction.           .        .  275 

Sec.  1.  Fermentation.       .....  275 

2.  Puliefaclion.         .....  2S6 

"    III.— Components  of  tee  Ahimal  Bodt.    .         .         .  292 

«    IV.— Animal  Heat   297 

Sec.  1.  Food.         ....         I         .  306 

2.  Hunger.      ....  311 

«      v.— Sleep.       .......  315 

«    VI.— Acids   317 

VII.— Oils   320 

"  VIII.— Antidotes  for  Poisons.  .         .        .  .324 

part  v.— meteorology. 

CHAP.  I.— Atmosphere.      ......  327 

"  II.— Winds   336 

Sec.  1.  Trnde  winds.         .....  342 

2.  Monsoons             .....  346 

«    III.— Clouds.     .         .         ,         .         .         ,         .  a56 

Sec.  1.  Modification  of  clouds   269 

2.  Dew.   374 

3.  Rain,  Snow,  Hail.           ....  388 

4.  Mist,  Fog,  Frost.            .         .         .     '     .  399 
«    IV,— Ice   413 

PART  VI.— OPTICS. 

eilAP.  I  —Light  .427 

Sec.  1.  The  eye  the  seat  of  vision.        •         .         ,  452 

2.  Deceptions  of  vision.       ....  458 

«      II.— Refk  action.       ......  tei 

"      III.— REFLECTIOJSf.          ......  473 

«    IV.— Color   477 

PART  VIL— SOUND. 

CHAP.  I  —Transmission  op  sound.         .        .        •         t  485 

jb'ec.  1.  Musical  sounds.     .         .         •         •         «  496 

2.  Echo  *  ,499 


MISCELLANEOUS.  .         .        .        .        *         .  flW 


PART  I.-HEAT, 


CHAP.  L— THE  SUN. 

BS«riONI.  THE  SUN  THE  PRIMARY  SOURCE  OF  HBAT 

1. 

Q.  What  is  heati 

A.  The  sensation  of  warmth. 

2. 

Q,  What  is  the  principal  source  of  heat  ? 
A.  The  Sun  is  an  inexhaustible  source  of 
heat. 

3. 

Q.  Does  the  heat  of  the  Sun  possess  any 
different  properties  from  artificial  heat  ? 

A.  The  heat  of  the  Sun  passes  readily 
through  glass,  whereas  this  property  is  pos- 
sessed by  artificial  heat  in  a  vei^y  small  de*  - 
^ree. 

4. 

Q.  Is  sun-shine  detrimental  to  combus- 
tion? 

A.  It  is;  the  reason  is  not  cerfaiinly 
7 


8 


THE  SUN. 


kn.  i^vri  ,  but  fires  are  never  so  bright  when 
ti;--:  .  'm  shines  on  tliem.  It  is  generally 
-  ^  posed  some  chemical  effect  is  proclucfMi 
vi[>un  the  Mr  in  contact  with  the  fire  which 
>Mj>Hdes  tlio  progress  of  combustion. 


SECTior;  II.  CALORIC. 


5. 

Q.  How  is  the  sensation  of  heat  produced  ? 

A.  When  Ave  touch  a  substance  hotter 
than  ourselves,  a  subtle  invisible  stream  flows 
from  the  hotter  substance^  and  produces  on 
our  nerves  the  sensation  of  warmth. 

6. 

Q.  What  is  that  ''subtle  invisible  stream^^ 
called,  which  flows  from  the  hotter  sub- 
stance ? 

A.  Caloric.  Caloric,  j:herefore  is  the 
agent,  which  produces  the  sensation  of 
warmth ;  but  heat  is  the  sensation  itself. 

7. 

Q.  Is  caloric  equally  distributed  over  thf! 
globe  ? 

A  No  ;  at  the  equator  the  average  tempe- 


CALORIC. 


9 


^ature  h  82i%  while  at  the  pole»  it  is  be- 
haved to  be  about  IS""  below  Zero. 

Average  Temperature,^''  that  is,  the  mean. or  medium  tempenttiirg'. 

Zero,"  the  point  I'tora  which  a  thermometer  is  graduated— St  i32* 
ow  freezing. 


CHAP.  II.— ELECTRICITY,  THE  SECOND 
SOUECE  OF  HEAT. 

SECTION  1.  ELECTRICITY  PRODUCED  BY  FRICTIOfiT. 

0. 

Q.  Was  electricity  known  to  the  ancients? 

A.  Yes ;  they  knew  that  when  amber  (the 
Greek  word  of  which  is  ?7^£xr(po^'— electron,) 
is  ruhhedy  it  acquires  the  property  of  attract- 
ing other  bodies. 

9. 

Q.  Why  is  electricity  excited  by  fncticn  ? 

A.  Electricity,  like  heat,  exists  in  all 
matter;  but  it  is  often  in  a  latent  state ; 
friction  disturbs  if,  and  brings  it  into  active 
peration. 

^Latenij^^ — that  is  hiiiden,  concealed. 

10. 

Q.  When  you  rub  a  piece  of  paper  with 
Indian  rubber,  why  does  it  adhere  to  the  ta- 
ble? 


10 


ELECTRICITY. 


A.  Because  the  friction  of  the  Indiari 
cnMj'jr  against  the  surface  of  the  paper  de- 
ve.l6|j^s  electricity,  to  which  this  adhesive- 
noiss  is  mainly  to  be  attributed. 

11. 

Q.  If  you  dry  a  piece  of  common  hrown 
foper  by  the  fire,  and  draw  it  once  or  twice 
between  your  knees,  why  will  it  stick  fast 
to  the  wall  ? 

A.  Because  the  friction  developes  electri- 
city on  the  paper,  which  manifests  itself  by 
this  proj)erty  of  adhesion. 

12. 

Q.  When  a  glazier  is  mending  a  window 
and  cleans  the  pane  with  his  brush,  why 
do  the  loose  pieces  of  putty  (on  the  opposite 
side  of  the  window  pane,)  dance  up  and 
down  ? 

A.  "\^T[ien  glass  is  rubbed,  electricity  is 
excited  in  the  parts  submitted  to  the  fric* 
Hon,  and  on  the  part  opposite  also;  electricity 
attracts  light  substances  such,  as  loose  frag- 
ments of  putty;  as  soon  as  these  fragments 
have  touched  the  excited  part  of  the  glas^ 
they  become  charged,  and  fall  back  agairlj 
the  ledge  on  which  they  fall  deprives  them 
of  their  burden,  and  they  then  fly  up  again 
to  receive  a  fresh  charge;  this  proceSjS  being 


PRODUCED  BY  FRICTION.  11 


1^3  pea  ted  often,  makes  the  commotion  in  tlie 
loose  fragments  of  putty,  referred  to  in  the 
question. 

13. 

Q.  Why  does  hrusJung  the  hair  for  a  long 
ime,  frequently  make  the  head  itch. 

A.  1st. — ^Because  the  friction  of  the  hair 
brush  excites  electricity  in  the  hair,  Avhich 
thus  becomes  overcharged  and  irritates  the 
skin;  and 

2nd. — The  hair  brush  excites  increased 
action  in  the  vessels  and  nerves  of  the  scalp, 
producing  a  slight  degree  of  inflammation, 
which  is  indicated  b  ^  a  sensation  of  itchin<?. 

14. 

Q.  "\Yhy  do  cats  rub  their  ears  when  it  is 
likely  to  rain? 

A.  Either  because  the  air  is  full  of  vapor 
and  its  humidity  (piercing  between  the  hair 
cf  the  c^i)  produces  an  itching  sensation:  or 
more  probably  because  the  air  is  overcharged 
with  ekctricity. 

15. 

Q.  How  can  the  electricity  of  the  air  pro* 
duce  a  sensation  itching? 

A.  If  the  air  is  overcharged  with  electricity 
the  hair  of  the  cat  is  overcharged  also;  fir^ 


12 


ELECTRICITY. 


this  makes  her  feel  as  if  she  were  cohered 
with  cobwebs. 

16. 

Q.  Why  does  the  cat  keep  rubbing  herself? 

A.  Because  her  hair  will  not  lie  smooth^  but 
has  a  perpetual  tendency  to  become  ruffled: 
so  the  cat  keeps  rubbing  her  coat  and  ears, 
to  smooth  the  hair  down,  and  brush  away  the 
feeling  of  cobwebs.  , 

17. 

Q.  Does  electricity  present  any  appear- 
ance by  which  it  can  be  known  ? 

A.  No;  electricity  like  heat,  is  in  itself 
invisible;  though  often  accompanied  by  both 
light  and  heat. 

18. 

Q.  Is  electricity  accompanied  with  any 
odor. 

A.  Yes;  near  a  large  electrical  machine 
in  good  action,  there  is  always  a  peculiar 
odor,  resembling  sulphur  and  phosphorus  ^ 
this  odor  is  called  "Ozone.'' 

19. 

Q  Has  this  peculiar  odor  called  ^^Ozone^^ 
been  observed  in  thunder  storms? 

A.  Yes;  sometimes  the  sulphurous  odoi 
prevails,  and  sometimes  the  phosphoric. 


LIGHTNINa. 


13 


20. 

Q.  Why  are  there  different  color b  in  the 
Aurora  Borealis,  such  as  white,  yellow,  red 
»i  lid  purple  ? 

A.  Because  the  electric  fluid  passes 
ih  rough  air  of  different  densities.  The  most 
rajified  air  produces  a  white  light ;  the  most 
iZ/  y  air,  red;  and  the  most  (/am^t?  produces 
yellow  streaks. 


SECTION  H.  LIGHTNING. 

21. 

Q.  What  is  lightning  ? 
A.  Lightning  is  accumulated  electricity  dis- 
charged/rom  the  clouds. 

Like  that  from  a  "  Leyden  jar." 

22. 

Q.  What  produces  electricity  in  the  clouds  f 
A.  1st. — The  evaporation  from  theearth^s 
surface ; 

2nd. — The  chemical  changes  which  take 
place  on  the  earth's  surface ;  and 

3rd. — Currents  of  air  of  unequal  tempera^ 
lure,  which  excite  electricity  hy  friction,  as 
they  come  in  contact  with  each  other. 
2 


14 


ELECTRICITY. 


23. 

Q.  What  causes  the  discharge  of  an  elec« 
trie  cloud? 

A.  When  a  cloud,  overcharged  with  elec» 
trie  fluid,  approaches  another  which  is  im- 
dercharged,  the  fluid  rushes  from  the  former 
into  the  latter,  till  both  contain  the  same 
quantity. 

There  are  two  different  kinds  of  Electricity — one  Vitreous,  andiTie  ether 
Resinous  :  more  frequently  called  Positive  and  Negative  Electucity. 

24. 

Q.  Is  there  any  other  cause  of  Lightning 
besides  the  one  just  mentioned  ? 

A.  Yes ;  sometimes  mountains,  trees, 
and  steeples,  will  discharge  the  lightning 
from  a  cloud  floating  near ;  and  sometimes 
electric  fluid  rushes  out  of  the  earth  into  the 
clouds. 

25. 

Q.  How  high  are  the  lightning  cloude 
from  the  earth? 

A ,  Sometimes  they  are  elevated  four  or 
five  miles  high ;  and  sometimes  actually 
touch  the  earth  with  one  of  their  edges  ;  but 
they  are  rarely  discharged  in  a  thunder 
storm,  when  they  are  more  than  se^'en  hiiri' 
ired  yards  above  the  surface  of  the  eaith 


uaHTNiNa. 


15 


26. 

Q.  How  high  are  the  clouds  generally? 

A.  In  a  fine  day,  the  clouds  are  often  four 
or  five  miles  above  our  heads;  but  the  average 
height  of  the  clouds  is  from  one  and  a  half 
to  two  miles. 

27. 

Q.  Why  is  lightning  sometimes  forked? 

A.  Because  the  lightning-cloud  is  at  a 
great  distance  ;  and  the  resistance  of  the  air  is 
so  great,  that  the  electrical  current  is  diverted 
into  a  zig-zag  course. 

28. 

Q.  How  does  the  resistance  of  the  air 
make  the  lightning  zig-zag? 

A.  As  the  lightning  condenses  the  air  in 
the  immediate  advance  of  its  path,  it  flies 
from  side  to  side,  in  order  to  pass  where 
there  is  the  least  resistance. 

29. 

Q.  Why  are  there  sometimes  two  flaphei^ 
of  forked  lightning  at  the  same  moment? 

A.  Because  (in  very  severe  storms)  the 
flash  will  divide  into  two  or  more  parts  ;  each 
of  which  will  assume  the  zig-zag  form. 

30. 

Q.  Why  is  the  flash  sometime^^  quite 
nraight? 


16 


ELECTRICITY. 


A.  Because  the  lightning-cloud  is  mar  tki 
earth ;  and,  as  the  flash  meets  with  very 
little  resistance,  it  is  not  diverted  ;  (in  other 
words)  the  flash  is  straight. 

31 

Q.  What  is  sheet  lightning? 

A.  Either  the  reflection  of  dhtant  flash  *s 
not  distinctly  visible,  or  beneath  the  hori- 
zon ;  or  else  several  flashes  intermingled. 

32. 

Q.  What  other  form  does  lightning  occa- 
sionally assume? 

A.  Sometimes  the  flash  is  g-/o&2//«r;  which 
is  the  most  dangerous  form  of  lightning. 

33. 

Q.  Why  is  a.  flash  of  lightning  generally 
followed  by  pouring  rain? 

A.  The  flash  produces  a  change  in  the 
physical  condition  of  the  air,  rendering  it  un- 
able to  hold  so  much  water  in  solution  as  it 
could  before ;  in  consequence  of  which,  a 
part  is  given  oS  in  heavy  rain. 

34. 

Q.  Why  is  a  flash  of  lightning  generally 
followed  by  a  gust  of  wind? 

A  Because  th e  physical  condition  of  the 


LIGHTNING. 


17 


is  disturbed  by  the  passage  of  the  Ughtuing, 
and  wind  is  the  result  of  this  disturbance. 

3-. 

Q.  Why  is  there  no  thvn(kr  to  what  is 
called  summer  lightning? 

A.  Because  the  lightning-clouds  are  so 
far  distant,  that  the  sound  of  the  thunder  is 
lost  before  it  reaches  the  ear. 

36. 

Q.  When  lightning  flashes  from  the  earth 
to  the  clouds,  what  is  the  flash  called  ? 

A.  It  is  popularly  called  the  ''returning 
stroke  because  the  earth  (being  over- 
charged with  electric  fluid,)  returns  the  sur- 
plus quantity  to  the  clouds. 

37. 

Q.  Why  is  lightning  more  common  in 
summer  and  in  autumn  than  in  spring  and 
winter? 

A.  Because  the  heat  of  summer  and 
autumn  produces  great  evaporation  ;  and  the 
inversion  of  water  into  vapor  always  de- 
velopes  electricity. 

33. 

Q.  Why  is  a  tree  sometimes  scorched  by 
lightning,  as  if  it  had  been  set  on  fire? 

A.  The  electric  fluid  scorches  by  its  own 
positive  he-'t,  just  the  same  as  fire  would. 
2* 


18 


ELECTlliaTf. 


39. 

Q.  When  does  lightning  pa^s  from  th 
earth  to  the  clouds? 

A.  When  the  clouds  are  ni  a  "negative"' 
«tate  of  electricity. 

40. 

Q.  When  does  lightning  pass  from  ihi 
clouds  to  the  earth? 

A.  When  the  clouds  are  in  a  "positive'^ 
state  of  electricity. 

41. 

Q.  What  is  meant  by  the  clouds  being  in 
a  ''positive  state  of  electricity?'' 

A.  When  the  clouds  contain  more  electric 
fluid  than  they  generally  do,  they  are  said  to 
be  in  a  "positive  state  of  electricity." 

42. 

Q.  What  is  meant  by  the  clouds  being  in 
a  "negative  state  of  electricity?'' 

A.  When  the  clouds  contain  less  electric 
fluid  than  they  generally  do ;  they  are  said 
to  be  m  a  "negative  state  of  electricity." 

43 

Q  Does  the  flash  proceed  from  a  negative. 
or  positive  body? 

A.  Always  from  a /lo^/fzt;^  body  :  that  ijfi 
from  one  over-charged  with  electric  fluid 


DANGER  FROM  LiailTNlNO. 


19 


§  I.—  Danger  from  Lightning. 
44. 

*    Q.  Why  does  lightning  sometimes  kill  men 
beasts? 

A.  Because,  when  the  electric  current 
passes  through  a  man  or  beast,  it  produces 
bc  violent  an  action  upon  the  nerves,  that  it 
destroys  life. 

45. 

Q.  When  is  a  person  struck  d.ead  by  light- 
ning? 

A.  Only  when  his  body  forms  a  part  of 
the  lightning^ s path;  that  is,  when  the  electric 
fluid  (in  its  way  to  the  earth)  actually  pas- 
ses through  his  body. 

46. 

Q.  Why  are  persons  sometimes  maimed  by 
lightning? 

A.  Because  the  electric  fluid  produces  an 
action  upon  the  nerves  sufficient  to  injure  them, 
but  not  to  destroy  life. 

47. 

Q.  Lightning  sometimes  assumes  the  ap- 
pearance of  balls  of  fire  which  fall  to  the 
earth,  what  are  they? 

A .  Masses  of  explosive  gas  formed  in  the 
air;  they  generally  move  more  slowly  than 
lightning. 


20       f-/  ELEtrnuciTY. 

48. 

Q.  Why  are  these  balls  of  fi*e  so  very 
danger  cms  1 

A.  Because  when  they  fall  they  explode 
like  a  camion;  and  occasion  much  mischief. 

49. 

Q.  Do  these  balls  of  fire  ever  run  along 
the  ground? 

A.  Yes;  sometimes  they  run  a  considera- 
ble distance  along  the  ground,  and  explode 

in  a  mass. 

At  other  times  they  split  into  numerous 
smaller  balls,  each  of  which  explodes  in  a 
similar  manner. 

50. 

Q  What  mischief  do  these  balls  of  fire 
produce  ? 

A.  They  set  fire  to  houses  and  bams,  and 
kill  all  cattle  and  human  beings  which  hap- 
pen  to  be  in  their  course. 

51. 

Q.  What  places  are  most  dangerous  during 
a  thunder  storml 

A.  It  is  very  dangerous  to  be  near  a  tree, 
or  lofty  building;  and  also  to  be  near  a 
river,  or  any  running  water. 

52. 

Q.  Why  is  it  dangerous  to  be  near  a 


DANGER  FROM  LtGHTNlNG. 


21 


tree  or  lofty  building,  during  a  thundei 
storm? 

A.  Because  a  tall  pointed  object  (like  f\ 
tree  or  spire)  will  frequently  discharge  » 
lightning-cloud ;  and  if  any  one  were  stand 
ing  near,  the  lightning  might  diverge  from 
the  tree,  and  pass  through  the  fluids  of  the 
human  body. 

53. 

Q.  How  can  a  tree  or  spire  discharge  a 
lightning-cloud  ? 

A.  A  lightning-cloud  (floating  over  a 
plain)  may  be  too  far  off  to  be  discharged  by 
it,  but  as  a  tree  or  spire  would  shorten  this 
distance,  it  might  no  longer  be  too  far  off 
to  be  discharged 

For  example;  If  a  lightning-cloud  were  700  yards  above  the  earth,  it 
would  be  too  far  off  \o  be  discharged  : — but  a  tree  or  spire  50  yards  high 
would  make  the  cloud  only  650  yards  off  a  conductor;  in  consequence  o< 
which  the  cloud  would  be  instantly  discharged. 

54 

Q.  Why  is  it  dangerous  to  be  near  a  deep 
river ^  or  any  other  running  water  during  a 
thunder  starm? 

A.  Because  running  water  is  a  good  con* 
ductor;  and  lightning  always  takes  in  ite 
course  the  best  conductors, 

55. 

Q.  Wliy  is  it  dangerous  for  a  ma,n  fco  be 
near  water  in  a  thunder  storm? 


ELECTRICITY. 


A.  Beccause  the  height  of  a  man  maj  h^t 
Fufllcient  to  discharge  a  cloud;  and  (if  there 
were  no  taller  object  nigh)  the  lightning 
might  make  the  man  its  conductor  to  the 
water 

56. 

Q.  Why  is  it  dangerous  to  ring  church  hells 
during  a  thunder  storm? 

A.  For  two  reasons;  1st.  Because  the 
steeple  may  discharge  the  lightning-cloud 
merely  from  its  height ;  and 

2nd. — As  the  swinging  of  the  bells  puts 
the  air  in  motion,  it  diminishes  its  resistance 
to  the  electric  fluid. 

57 

Q.  Wh}'  is  it  unsafe  to  run  or  drive  fast 
during  a  thunder  storm? 

A.  Because  it  produces  a  current  of  air ; 
and,  as  air  in  motion  affords  less  resistance  to 
the  flash,  it  is  a  better  conductor  than  ai^ 
in  a  state  of  rest. 

58. 

Q.  What  parts  of  a  dwelling  are  most  dan- 
gerous during  a  thunder  storm? 

A.  The  fire-place,  especially  if  the  fire  be 
lighted  ;  the  attics  and  the  cellar.  It  is  also 
imprudent  to  sit  close  by  the  walls ;  to  ring 


DANGER  FROM  LIGHTNING.  23 


the  bell,  or  to  bar  the  shutters  during  a 
thunder  storm. 

59. 

Q.  Why  is  it  dangerous  to  sit  heforj^  a  fis  e, 
during  a  thunder  storm? 

A.  Because  the  heated  air  and  soot  aru 
coiidtidors  of  lightning;  especially  when 
connected  with  such  excellent  conductors  as 
the  stove,  grate,  or  fire-irons. 

60. 

Q.  Why  are  attics  and  cellars  more  dan- 
gerous in  a  thunder  storm,  than  the  middle 
f?tory  of  a  house? 

A.  Because  lightning  sometimes  passes 
from  the  clouds  to  the  earth,  and  sometimes 
from  the  earth  to  the  clouds ;  in  either  case 
the  middle  story  would  be  the  safest  place.- 

61. 

Q.  Why  is  it  dangerous  to  lean  against  a 
%?oU  during  a  thunder  storm? 

xV.  Because  the  electric  fluid  w^ill  some- 
iimes  run  down  a  wall ;  and,  (as  a  man  is  a 
better  conductor  than  a  w^all,)  w^ould  leave 
the  wall  and  run  down  the  man. 

62. 

Q.  Why  is  it  dangerous  to  ring  a  bell 
during  a  thunder  storm? 


24 


ELECTRICITY. 


A  Bell-wire  is  an  excellent  conductor,  and 
if  a  person  were  to  touch  the  bell  handle, 
the  electric  fluid,  passing  down  the  wire, 
might  run  through  his  hand  and  injure  it, 

63 

Q  Why  is  it  dangerous  to  bar  a  shutta 
luring  a  thunder  storm? 

A.  Because  the  iron  shutter-bar  is  an  ex- 
cellent conductor ;  and  the  electric  fluid  might 
run  from  the  bar  through  the  person  touching 
it,  and  injure  him. 

64. 

Q.  Why  is  it  dangerous  to  be  in  a  crowd 
during  a  thunder  storm? 

A.  For  two  reasons :  Because  a  mass  of 
people  forms  a  better  conductor  than  an  indi- 
vidual ;  and 

2nd. — Because  the  vapor  arising  from  a 
crowd  increases  its  conducting  power. 

65. 

Q.  Why  is  the  danger  increased  by  the 
vapor  which  rises  from  a  crowd? 

A.  Because  vapor  is  a  conductor ;  and  the 
more  conductors  there  are,  the  greater  the 
danger  will  be. 

66. 

Q.  Why  is  a  theatre  dangerous  during  a 
thunder  storm? 


DANGER  FROM  LIGHTNING.  25 

A.  Because  tlie  crowd,  and  great  vapor 
arising  from  so  many  living  bodies,  render 
it  an  excellent  conductor  of  lightning. 

67. 

Q.  Why  is  a  flock  of  sheep,  herd  of  cattle, 
etc,  in  greater  danger  than  a  smaller  num- 
ber? 

A.  1st. — Because  each  animal  is  a  con- 
ductor of  lightning,  and  the  conducting  pow- 
er of  the  flock  or  herd,  is  increased  by  its 
numbers;  and 

2nd. — The  very  vapor  arising  from  the 
flock  or  herd  increases  its  conducting  power 
and  its  danger. 

63. 

Q.  If  a  person  be  abroad  in  a  thunder 
storm,  what  place  is  the  safest? 

A.  Any  place  about  twenty  or  thirty  feet 
from  a  tall  tree,  building,  or  stream  of 
water. 

69. 

Q.  Why  would  it  be  safe  to  stand  twenty 
or  thirty  feet  from  a  tall  tree,  during  a 
thunder  storm? 

A.  Because  the  lightning  would  always 
cliuose  the  tall  tree  as  a  conductor;  and  we 
should  not  be  sufficiently  near  the  tree,  for 
the  lightning  to  diverge  from  it  to  us. 
3 


26 


ELECTRICITY. 


70. 

Q.  If  a  person  be  in  a  carriage,  in  a  Ihun 
dor  storm,  in  what  way  can  he  travel  moH[ 
safely  ? 

A.  He  should  not  lean  against  the  car 
riage,  but  sit  upright,  without  touching  any 
of  the  four  sides. 

71 

Q.  Why  should  not  a  person  lean  against 
the  carriage  in  a  storm? 

A.  Because  the  electric  fluid  might  run 
down  the  sides  of  the  carriage ;  and  (if  a 
person  were  leaning  against  them)  would 
make  a  choice  of  him  for  a  conductor,  and 
perhaps  destroy  life. 

72. 

Q.  If  a  person  be  in  a  house  during  a 
thunder  storm,  what  place  is  safest? 

A.  Any  room  in  the  middle  story.  Tho 
centre  of  the  room  is  the  best;  especialU^ 
if' you  place  yourself  on  a  mattrass,  bed,  or 
li^arth-rug. 

73. 

Q.  Why  is  the  middle  story  of  a  houso 
safest  in  a  thunder  storm? 

A.  Because  the  fluid  (if  it  struck  the 
house  at  all)  would  be  difiiised  among  the 
several  conductors  of  the  upper  part  of  tho 


D^VNGER  FROM  LIGIITNLNG. 


house,  before  it  reached  the  middle  story , 
in  consequence  of  which  its  force  would  bo 
weakened. 

74. 

Q/  Wh}^  is  the  middle  of  a  roo7n  more  safe 
than  any  other  part  of  it  in  a  thunder 
§torm? 

A.  Because  the  lightning  (if  it  should 
strike  the  room  at  all,)  would  come  down 
the  chimney  or  walls  of  the  room;  and,  there- 
fore, the  further  distant  from  these,  the 
better. 

75. 

Q.  Why  is  a  matt r ass,  bed,  or  hearth-rug,  a 
good  security  against  injury  from  lightnhig? 

A.  Because  they  are  all  non-conductors  ; 
and,  as  lightning  always  makes  choice  of  the 
hest  conductors,  it  would  not  choose  for  its 
path  such  things  as  these. 

76. 

Q.  What  is  the  safest  thing  a  person  can 
d(;  to  avoid  injury  from  lightning? 

A.  He  should  draw  his  bedstead  into  the 
middle  of  his  room,  commit  himself  to  the 
care  of  God,  and  go  to  bed  ;  remembering 
that  our  Lord  has  said,  "The  very  hairs  of 
your  head  are  all  numbered." 

\r>  jjreiit  dansrcr  need  really  to  he  appn^h^nded  from  'iffbtnin?,  if  yon 
avoid  lakiiig  your  posinou  near  tall  trees,  siurea,  or  other  elevated  otjeeta 


28 


ELECTRICITY. 


77. 

Q.  Is  it  better  to  be  wet  or  dry  during  a 
thunder  storm? 

A.  To  be  wet ;  if  a  person  be  in  tlie  open 
tield,  the  best  thing  he  can  do,  is  to  stand 
about  twenty  feet  from  some  tree,  and  get 
completely  drenched  to  the  skin. 

IB. 

Q.  Why  is  it  better  to  be  wet  than  dry? 

A.  Because  wet  clothes  form  a  letter  con- 
ductor than  the  fluids  of  our  body  ;  and  there- 
fore, lightning  would  pass  down  our  wet 
clothes,  without  touching  our  body  at  all. 

§  n. — Lightning  Conductor. 
79. 

Q.  WTiat  is  a  lightning  conductor? 

A.  A  metal  rod  fixed  in  the  earth,  run- 
ring  up  the  whole  height  of  a  building,  and 
rising  in  a  point  above  it. 

80. 

Q.  Wh^i  metal  is  best  for  this  purpose? 
A.  Copper  makes  the  best  conductor. 

81. 

Q.  Why  is  copper  better  than  iron? 
A.  1st. — Because  copper  is  a  better  con- 
ductor than  iron ; 


^  LIGHTNING  CONDUCTORS.  29 

2n(|^— It  is  not  so  easily  fused  or  melted ; 
and 

3rd. — It  is  not  so  readily  injured  by 
weather. 

82. 

(Jl  What  is  the  use  of  a  lightning  con- 
ductor? 

A.  As  metal  is  a  most  excellent  con- 
ductor, lightning  (which  makes  choice  of 
the  best  condudGrs)  will  run  down  a  metal 
rod,  rather  than  the  walls  of  the  building. 

S3. 

Q.  Why  should  liglitnmg-conductors  be 
pointed  ^ 

A.  Because  points  conduct  electricity 
away  silently  and  imperreptUdy ;  but  Ivuobs 
produce  an  explosion  which  w^ould  endanger 
the  building. 

P.)infs  empty  the  p'onds  of  electricity,  actinsrat  n  innch  ^renter  distanoia 
Ihriii  k  jolx  ;  f  liu*.  a  lievll^'Jl  jnr  «»f  consiHerahle  fsize  mny  l)e  sMfVly  and 
c-ilH.nIv  tli<<-harirefl,  by  holdiiii^  the  point  of  a  ii-^rdie  an  inch  or  iwo  o:T. 

Mbnlcj;  of  L'r  i<is,  ears  of  corn,  and  other  pointed  objecu  serve  lo  empty 
the  clouds  of  iheir  electricity. 

84. 

Q.  1'\o^Y  f ar  ^Y\\\  the  beneficial  influence 
cf  a  lightning-conductor  extend? 

A.  Tt  will  protect  a  space  all  round,  four 
times  the  length  of  that  part  of  the  ro'b 
vv'hich  rises  above  the  building. 
3* 


so 


ELECTRICITY. 


85.  ^ 

Q.  Give  me  an  example? 

A.  If  the  rod  rise  two  feet  above  tlie 
house,  it  will  jorotect  the  building  for  (at 
least)  eight  feet  all  round. 

86.  0 

Q,  How  can  lightning-conductors  be  pro- 
ductive of  harm? 

A.  If  the  rod  be  broken  by  weather  or 
accident,  the  electric  fluid  (being  obstructed 
in  its  path)  will  damage  the  building. 

87. 

Q.  Is  there  any  other  evil  to  be  appre- 
hended from  a  lightning-rod? 

A.  Yes  ;  if  the  rod  be  not  large  enough 
to  conduct  the  whole  current  to  the  earth, 
the  liglitning  will  fuse  the  metal,  and  injure 
the  building. 

88. 

Q.  ^¥lly  are  boughs  of  trees  broken  off  by 
lightning? 

A.  Because  the  mechanical  force  of  the 
lightning  is  very  great ;  and,  as  the  boughs 
of  a  tree  are  imperfect  conductors,  they  will 
often  be  broken  off  by  this  force. 

Q.  Why  is  an  electric  shock  felt  most  al 
the  elbow  joint? 


LIGHTiVlNG  CONDUCTORS.  31 

A.  Because  the  path  of  the  fluid  is  ob- 
structed by  the  joint ;  and  the  shock  (felt  at 
the  elbow)  is  caused  by  the  fluid  leaping 
from  one  bone  to  another.       ,  ^ 

90. 

Q.  Is  not  air  a  conductor  of  lightning? 
A.  No ;  dry  ^air  is  not  a  conductor  of 
lightning. 

91. 

Q.  Why  does  lightning  part  the  air 
through  which  it  passes  ?  it  does  not  part  a 
rod  of  iron. 

A.  As  iron  is  a  conductor^  it  allows  the 
fluid  to  pass  freely  through  it ;  but  air  (be- 
ing a  non-conductor,)  resists  its  passage. 

92 

Q.  ^Vhy  is  an  oak  struck  by  lightning 
more  frequently  than  any  other  tree? 

A.  Because  the  grain  of  the  oak,  being 
closer  than  that  of  any  other  tree  of  the  same 
bulk,  renders  it  a  better  conductor. 

It  i<5  said  that  the  sap  of  the  oak  contains  a  lar^e  quantity  of  iron  in  sola, 
lion,  which  irapregnaie*i  the  wood  and  bark,  thus  increasing  its  conducting 
power. 

93. 

Q  Does  lightning  go  through  the  inside 
or  down  the  outside  of  a  tree  ? 

A.  It  runs  down  the  outside  of  a  tjce,  but 
passes  through  the  imide  of  a  man. 


32 


ELECTRICITY 


^  94. 

Q.  Why  does  lightning  jmss  do^vn  the 
ouiside  of  a  tree? 

A.  Because  it  always  makes  choice  of 
tlic  best  conductors ;  and  the  outside  of  a  tree 
b  a  better  conductor  than  the  inside. 

95. 

Q.  Why  does  lightning  pass  through  the 
inside  of  a  man? 

A.  Because  the  fluids  of  the  human  body 
made  a  better  conductor  than  the  skin ; 
therefore,  lightning  passes  through  a  man, 
and  not  down  his  skin. 

96. 

Q.  Why  would  the  lightning  run  through 
a  man  touching:  a  bell  handle? 

A.  Because  the  human  body  is  a  better 
conductor  than  the  wall,  which  is  between 
the  bell  handle  and  the  floor ;  and  as  light- 
nins;  always  chooses  the  best  conductor  for 
its  path,  it  would  (in  this  case)  i:)ass  through 
the  ruan. 

97, 

^vliy  is  a  mass  of  bodies  a  better  con- 
dnclor  than  a  single  body? 

A.  Each  living  body  is  a  conductor  of 
electricity  ;  and  in  a  connected  mass  of  f.ucJi 


EFFECTS  OF  LIGHTNING 


33 


conductors,  is  more  likely  to  be  struck  than 

a  sinde  individual-, 

o 

98. 

Q.  Why  would  lightning  fly  from  a  tree 
or  spire  into  a  man  standing  near? 

A.  Because  the  electric  fluid  (called  lignfc- 
ning)  always  chooses  for  its  path  the  h^st 
conductors  ;  and,  if  the  human  fluids  proved 
the  better  conductor,  it  would  pass  through 
the  man  standing  near  the  tree,  rather  than 
down  the  tree  itself. 

There  would  be  no  daiio^er  if  i*he  spire  were  made  of  metal;  becau£fl 
metal  is  a  belier  conductor  than  the  human  fluids. 

§  lu.— Effects  of  Lightning.  "  ^  ^^^^ 
99. 

Q.  Whatai^e  fulgurites?  , 

A.  Hollow  tubes  produced  in  sandy  soils 

by  the  action  of  lightning. 

100. 

Q.  How  does  lightning  produce  fulgurites? 

A.  When  it  enters  the  earth,  it  fuses, 
(that  is,  melts)  the  flinty  matter  of  the  soil 
into  a  vitreous  (or  glassy)  substance,  called 
a  fulgurite. 

101 

Q.  Why  is  the  hark  of  a  tree  often  ripped 
quite  off  by  a  flash  of  lightning?  ^ 


SI  ELECTRICITY. 

A.  Because  the  latent  heat  of  the  tree 
(being  very  rapidly  developed  by  the  elec- 
tric thiid)  forces  away  the  bark  in  its  iiri' 
peiaosity  to  escape. 

Pnme  pari  of  ihis  is  probably  due  to  the  simple  mechanical  fcrce  of  the 
1C2. 

Q.  How  does  lightning  sometimes  knock 
down  houses  and  churches? 

A.  The  steeple,  or  chimney  is  first  struck; 
the  lightning  then  darts  to  the  iron  bars 
and  cramps  employed  in  the  building ;  and 
(as  it  darts  from  bar  to  bar)  shatters  to  atoms 
the  bricks  and  stones  which  oppose  its  pro- 
gress. 

103. 

Q.  Can  you  tell  me  liow  St.  Bride's 
church,  (London,)  was  nearly  destroyed  by 
lightning,  about  one  hundred  3'ears  ago? 

A.  The  lightning  first  struck  the  metal 
vane,  nnd  ran  down  the  rod  ;  it  then  darted 
to  the  iron  cramps,  employed  to  support 
the  building;  and  (as  it  ilew  fronj  bar  Id 
bar)  smashed  the  stones  of  the  churcl), 
which  lay  between. 

104. 

Q.  Why  did  the  lightning  fly  about  from 
place  to  place? 


EFFECTS  OP  LIGHTNING. 


A.  Because  it  jilwcays  takes  in  its  course 
Hie  hist  conductors  ;  and  will  fly  both  right 
and  left,  in  order  to  reach  them, 

105. 

Q.  Why  does  lightning  turn  milk  sour? 

A.  Lightning  causes  the  gases  of  the  air 
(through  which  it  passes)  to  combinCy  and 
thus  produces  a  poison,  called  nitric  acid  ; 
Bome  small  portion  of  wdiich,  mixing  with 
the  milk,  turns  it  sour.* 

N.  B.  Sometimes  the  mere  heat  of  the  air,  during  the  storm,  turns  milk 
sour. 

106. 

Q.  What  is  the  difference  between  com- 
bining; and  mixing!;? 

A.  When  different  ingredients  are  min- 
gled together  without  undergoing  ani/  chemical 
change^  they  are  said  to  be  mixed  ;  but  when 
the  natural  properties  of  each  are  altered  by 
the  union,  then  those  ingredients  are  said  to 
be  combined. 

107. 

Q   Give  me  an  example? 
A.  Different  colored  sands  (shaken  to- 
gether in  a  bottle)  will  mix,  but  not  com- 

*  T.ieair  is  fomn"»sp(1  of  two  jrasoi,  called  oxy2"*»n  and  nitropren^  mixeii 
tnsrcth«^r.  but  not  cnmbhip.d.  Oxygen  combined  with  nitri-fjen,  producet 
five  deidly  poi.-son-s,  viz: — nitron*  oxide,  nitric  oxifle,  byponitrous  a.-;id, 
nitron;*  acid,  and  nitric  acid,  according.to  the  proporiion  of  each  gas  in  th« 
tombination 


36 


ELECTRICITY. 


bine ;  but  water  poured  on  quick-lime,  will 
tomhiiie  with  the  lime  and  not  mix  with  it.. 

108. 

Q.  Why  are  different  grains  of  sand  said 
(o  be  mixed  when  they  are  shaken  together? 

A  Because  (though  mingled  together^ 
the  property  of  each  grain  remains  the  same 
as  it  was  before. 

109. 

Q.  Wliy  is  water,  poured  on  lime,  said  to 
combine  with  it? 

A.  Because  the  properties  of  each  are 
altered  by  the  mixture  ;  the  Ume  alters  the 
character  of  the  water,  and  the  water  that 
of  the  lime. 

110. 

Q.  Do  oxygen  and  nitrogen  combine,  or 
(mly  mix  together  in  atmospheric  air  ? 

A.  They  only  mix  together,  as  grains  of 
sand  would  do,  when  shaken  in  a  bottle. 
When  oxygen  and  nitrogen  combine,  they  do 
not  constitute  air,  but  acid  poisons. 

111. 

Q.  Why  does  lightning  turn  beer  sour  al- 
though contained  in  a  close  cask  ? 

A.  Because  if  beer  be  new  and  the  pro- 
cess of  fermentation  incomplete,  lightning 
tvill  so  accAerate  the  process,  as  to  turn  the 


EFFECTS  OF  LIGHTNINa 


BUgar  into  acetic  acid  at  once,  without  pass- 
ing through  the  intermediate  state  of  alco- 
hol. 

112. 

Q.  Why  is  not  old  beer  and  strong  porter 
made  sour  by  lightning  ? 

A.  Because  the  fermentation  is  more 
complete  ;  and,  therefore,  is  less  affected  by 
electrical  influence. 

113. 

Q.  Why  is  metal  sometimes  fused  by 
lightning  ? 

A.  Because  the  dimension  of  the  metal 
is  too  small  to  afford  a  path  for  the  electric 
current. 

114. 

Q.  Why  does  lightning  purify  the  air  ? 

A.  For  two  reasons ; 

1st.  Because  the  electric  fluid  produces 
"  nitric  acid  in  its  passage  through  the 
air;  and 

2nd.  Because  the  agitation  of  the  storm 
stirs  up  the  air. 

The  "  nitric  ocid  "  is  produced  by  the  combination  of  Bom©  portions  of 
the  oxygen  and  nitrogen  of  the  air. 

115. 

Q,  How  does  the  production  of  nitrio 
acid  purify  the  air  ? 

4 


88  ELECTRICITY. 

A.  Nitric  acid  acts  very  powerfully  in  de 
stroi/ing  the  exhalations,  which  arise  from 
putrid  vegetable  and  animal  matters. 

116. 

Q.  Does  not  lightning  sometimes  afFcct 
the  character  of  iron  and  steel  ? 

A.  Yes ;  bars  of  iron  and  steel  are  some- 
times rendered  magnetic  by  lightning. 

117. 

Q.  Give  me  an  instance  of  the  magnetic 
effects  of  lightning  ? 

A.  Sometimes  it  will  reverse  the  needle 
of  the  magnet,  and  sometimes  destroy  its 
magnetism  altogether. 

113. 

Q.  What  is  meant  by  the  magnetic  needle 
being  reversed  ? 

A.  That  part  of  the  needle  which  ought 
to  point  toward  the  north,  is  made  to  point 
toward  the  south ;  and  that  part  which 
ought  to  point  south,  is  made  to  point  to- 
ward the  north. 

SECTION  ITI.  THUNDER. 

119. 

Q.  What  is  thunder? 

A.  The  noise  made  by  the  concussion  oi 


THUNDER. 


3S 


the  air  when  it  closes  again,  after  it  has  been 
parted  by  the  hghtning  flash. 

A  psirt  of  !he  jioi?e  is  owing  to  pertain  physical  and  chemical  changes  pro* 
daced  in  ihe  air  by  liie  electric  fluid. 

120. 

Q.  Why  is  thunder  sometimes  one  vast 
^rash ? 

A.  Because  the  lightning-cloud  is  near  the 
tarth  ;  and  as  all  the  vibrations  of  the  air, 
(on  which  sound  depends)  reach  the  ear  at 
the  same  moment^  thej^  seem  like  one  vast 
sound. 

121 

Q.  Why  is  the  peal  sometimes  an  irregu- 
lar broken  roar? 

A.  Because  the  lightning-cloud  is  at  a 
great  distance  ;  and  as  some  of  the  vibrations 
of  the  air  have  much  further  to  travel  than 
others,  they  reach  the  ear  at  different  times, 
and  jDroduce  a  continuous  sound. 

122. 

Q.  Which  vibrations  will  be  soonest 
heard? 

A.  Those  produced  in  the  lowest  portions 
of  the  air. 

123. 

Q,  Why  will  those  vibrations  be  heard 
first,  wdiich  are  made  last? 

A.  Because  the  flash  (which  produces  (he 


40 


ELECTRICITY. 


BOimd)  is  almost  instantaneous^  but  sound 
takes  a  whole  second  of  time  to  travel  throe 
hundred  and  eighty  yards.  ^ 

124. 

Q.  If  a  thunder-cloud  were  one  thousand 
nine  hundred  yards  off,  how  long  would  the 
peal  last? 

A.  Five  seconds;  we  should  first  hear  the 
vibrations  produced  in  those  portions  of  the 
air  contiguous  to  the  earth  ;  then  those  more 
remote  ;  and  it  would  be  five  seconds  before 
those  vibrations  could  reach  us,  which  were 
made  in  the  immediate  vicinity  of  the  cloud, 

380  X5=1900 

A  popular  method  of  telling  liow  far  off  a  storm  is,  is  this — The  moment 
you  see  the  fias-h  put  your  hand  upon  your  pulse,  and  coant  how  many 
times  it  beats  before  you  hear  the  thunder;  if  it  beats  six  pulj-ations,  the 
storm  is  one  mile  off  j  if  twelve  pulsations,  it  is  two  miles  off,  and  so  on. 

125 

Q.  Why  is  thunder  sometimes  like  a  deep 
growl? 

A.  Because  the  storm  is  far  distant^  and 
the  sound  of  the  thunder  indistinct. 

126. 

Q.  Is  not  the  sound  of  thunder  affected 
by  local  circumstances? 

A.  Yes ;  the  flatter  the  country  the  more 
imbroken  the  peal.  Mountains  break  the 
I)eal  and  malce  it  harsh  and  irregular. 


THUNDEK. 


41 


127. 

Q  What  is  the  cause  of  rolling  thunder  ? 

A.  The  vibrations  of  air  (having  different 
lengths  to  travel)  reach  the  ear  at  successive 
intervals. 

The  reverberation  (or  echo)  amongst  the  massive  clouds  contributes  la 
50ii.e  inca»ure  to  this  effect. 

128. 

Q.  Do  thunder-holts  ever  drop  from  the 
clouds  ? 

A.  No  ;  the  notion  of  thunder-bolts  arises 
either  from  the  globular  form  which  light- 
ning sv^metimes  assumes ;  or  else  from  the 
gaseous  fire-balls,  which  sometimes  fall  from 
the  clouds. 

See  question 
129. 

Q.  Why  is  the  thunder  often  several  mo- 
ments after  the  flash  ? 

A.  Because  it  has  a  Ions;  distance  to  tra- 
vel.  Lightning  travels  nearly  a  million 
times  fister  than  thunder ;  if,  therefore,  the 
thunder  has  a  great  distance  to  come,  it  will 
not  reach  the  earth,  till  a  considerable  time 
after  the  flash.  ^ 

130. 

Q.  Can  we  not  tell  the  distance  oi  a  thun- 
der-cloud, by  observing  the  interval  vdiicb 
elapses  between  the  flash  and  the  peal  ? 
4* 


42 


ELECTRICITY. 


A.  Yes ;  the  flash  is  instantaneous,*  but 
thunder  will  take  a  whole  second  of  time  tc 
travel  three  hundred  and  eighty  yards; 
hencQ,  if  the  flash  be  five  seconds  before 
the.  thunder,  the  cloud  is  nineteen  hundred 
yards  off*.  \ 

i.  e  380  X5=1900  yards. 
131. 

Q.  Why  does  a  thunder -storm  generally 
follow  very  dry  weather  ? 

A.  Because  dry  air  (being  a  non-conduc- 
tor) will  not  relieve  the  clouds  of  their 
electricity ;  so  the  fluid  accumulates,  till  the 
clouds  are  discharged  in  a  storm. 

132. 

Q.  Wliy  does  a  thunder-storm  rarely  suc- 
ceed wet  weather  ? 

A.  Because  moist  air  or  falling  rain  (be- 
ing a  conductor,)  carries  down  the  electric 
fluid  gradually  and  silently  to  the  earth. 

133. 

Q.  What  kind  of  weather  generally  pre- 
cedes a  thunder-storm  ? 

A.  It  is  generally  preceded  by  hot  wea- 
ther. 


*The  speed  of  lightning  is  so  great,  that  it  would  go  four  hundred  end 
eighty  times  round  the  earth  in  one  minute ;  whereas,  thander  would  g6 
•csrcely  thirteen  miles  in  the  same  space  of  lime. 


EXPANSION. 


43 


CHAP.  III.— CHEMICAL  ACTION,  THE 
THIKD  CHIEF  SOURCE  OF  HEAT. 

134. 

Q.  What  is  meant  by  chemical  action  be- 
ing the  source  of  heat? 

A.  Many  things,  when  their  cliemical 
constitution  is  changed,  (either  by  the  ab- 
straction of  some  of  their  gases,  or  by  the 
combination  of  others  not  before  united) 
evolve  heaty  while  the  change  is  going  on. 

SECTION  I.  EXPANSION. 

135. 

Q.  What  effect  has  heat  upon  substances 
generally? 

A.  It  expands  them,  or  enlarges  their  di- 
mensions. 

§  I. — Expansion  of  Liquids  and  Gases. 
136. 

Q.  Does  heat  expand  air  ? 

A.  Yes;  if  a  bladder  (partially  filled  with 
air)  be  tied  up  at  the  neck,  and  laid  before 
the  fire,  the  air  will  expand  till  the  bladder 
bursts. 

137. 

Q.  ^Vhy  will  the  air  sivell  if  the  bladder 
be  laid  before  the  fire? 


i4: 


CHEMICAL  ACTIO]S. 


A.  Because  the  heat  of  the  fire  will  drive 
the  particles  of  air  apart  from  each  other,  and 
cause  them  to  occupy  more  room  than  tliey 
did  before. 

138. 

Q.  Does  heat  expand  everything  else  be- 
sides air  and  water? 

A.  Yes ;  every  thing  (that  man  is  ac- 
quainted with)  is  expanded  by  heat. 

139. 

Q.  Why  do  unslit  chestnuts  crack  with  a 
loud  noise  w^hen  roasted? 

A.  Because  they  contain  a  great  deal  of 
air  which  is  expanded  by  the  heat  of  the 
fire ;  and  not  being  able  to  escape,  bursts 
violently  through  the  thick  rind,  slitting  z7, 
and  maldng  a  great  noise. 

140. 

Q.  What  occasions  the  loud  crack  or  re- 
port which  w^e  hear? 

A.  1st. — The  sudden  bursting  of  the  shell 
makes  a  report,  in  the  same  way  as  a  piece 
of  wood  or  glass  would  do,  if  snapped  in  two  ; 
and 

2nd. — The  escape  of  hot  air  from  the 
chestnut  makes  a  report  also  ;  in  the  same 
way  as  gunpoiuder^  when  it  escapes  from  a 
^un. 


EXPANSION  OF  LIQUIDS  AND  GASES.  45 
141. 

Q.  Why  does  the  sudden  hurstmg  of  the 
ehell,  or  snapping  of  a  piece  of  wood,  make 
a  report? 

A.  Because  a  violent  jerk  is  given  to  the 
air,  when  the  attraction  of  cohesion  is  thus 
suddenly  overcome.  This  jerk  produces 
rapid  undulations  in  the  air,  which  (striking 
upon  the  ear)  give  the  brain  a  sensation  of 
sound. 

142. 

^  Q.  Why  does  the  escape  of  air  from  the 
chestnut,  or  the  explosion  of  gunpowder y  pro- 
duce  a  report? 

A.  Because  the  sudden  expansion  of  the 
imprisoned  air  produces  a  partial  vacuum  ; 
the  report  is  caused  by  the  rushing  of  fresh 
air  to  fill  up  this  vacuum. 

143. 

Q.  If  a  chestnut  be  slity  it  will  not  crack  ; 
why  is  this? 

A.  Because  the  heated  air  of  the  chestnut 
can  then  freely  escape  through  the  slit  in  the 
rind. 

144. 

Q.  \Yhy  does  an  apple  split  and  spurt 
about  when  roasted? 

A.  Because  it  contains  a  vast  quantity  of 


46 


CHEMICAL  ACTION. 


ai7\  whicli  (being  expanded  by  the  heat  r)f 
the  fire)  bursts  through  the  peel,  carrymg  the 
juice  of  the  apple  along  with  it. 

145. 

Q.  Does  an  apple  contain  more  air  in  pro* 
portion  than  a  chestnut? 

A.  Yes,  much  more.  There  is  as  much 
condensed  air  in  a  common  apple,  as  would 
fill  a  space  forty-eight  times  as  large  as  the 
apple  itself. 

146. 

Q.  How  can  all  this  air  be  stowed  in  an 

apple? 

A.  The  inside  of  an  apple  consists  of  little 
cells  (like  a  honey-comb,)  each  of  which 
contains  a  portion  of  air. 

147. 

Q.  When  an  apple  is  roasted,  w^hy  is  one 
part  made  softy  w^liile  all  the  rest  remains 
hard? 

A.  Because  the  air  in  those  cells  next  the 
fire  is  expanded,  and  flies  out ;  the  cells  are 
broken,  and  their  juices  mixed  together ;  so 
the  apple  collapses  {from  loss  of  air  and  juice,) 
and  feels  soft  in  those  parts. 

148. 

Q.  What  is  meant  by  the  "apple  collaps* 
ingr 


EXPANSION  OF  LIQUIDS  AND  GASES. 


47 


A.  It  means  that  the  plumpness  gives  way, 
and  the  apple  becomes  flabby  and  shriveled. 

149. 

Q.  Why  do  sparks  of  fire  start  (witli  a 
crackling  noise)  from  pieces  of  wood  laid 
upon  a  fire? 

A.  Because  the  air  {expanded  by  the  heat) 
forces  its  way  through  the  pores  of  the  wood  ; 
and  carries  along  with  it  the  covering  of  the 
pore,  which  resisted  its  j^assage. 

159. 

Q.  What  is  meant  by  the  ''pores  of  the 
wood?'^ 

A.  Very  small  holes  in  the  woody  through 
which  the  sap  circulates. 

151. 

Q.  What  are  the  sparks  oj  fire  which 
burst  from  the  woodl 

A.  Very  small  pieces  of  wood  made  red 
hot,  and  sej)arated  from  the  log  by  the  force 
of  the  airy  when  it  bursts  from  its  confine- 
ment 

152. 

Q.  Why  does  light  porous  wood  make  more 
snapping  than  any  other  kind? 

A.  Because  the  pores  are  very  large,  and 
contain  more  air  than  wood  of  a  close?  grain. 


48 


CHEMICAL  ACTION. 


153. 

Q.  Why  does  green  wood  make  less  snap* 
ping  than  dry? 

A.  Because  the  pores  being  filled  with 
sap,  contain  very  little  air. 

154. 

Q.  Why  does  dry  wood  make  more  snap- 
ping than  green? 

A.  Because  the  sap  is  dried  up,  and  the 
pores  are  filled  with  air  instead. 

155 

Q.  Wliy  does  dry  wood  burn  more  easily 
than  green  or  wet  wood? 

A.  Because  the  pores  of  diy  wood  are 
filled  with  air  which  supports  combustion ; 
but  the  pores  of  green  or  wet  wood  are  filled 
with  moisture,  which  extinguishes  flame. 

156. 

Q.  Why  does  moisture  extinguish  flame  ? 

A.  1st. — Because  it  prevents  the  hydrogen 
of  the  fuel  from  mixing  with  the  oxygen  of 
the  air,  to  form  carbonic  acid  gas  ;  and 

2nd. — Because  heat  is  perpetually  carried 
off,  by  the  formation  of  the  sap  or  mois 
ture  into  steam. 

157. 

Q.  Why  do  stones  snap  and  fly  about  when 
heated  in  the  fire  ? 


EXPANSION  OF  LIQUIDS  AND  GASES.  49 

A.  Because  the  close  texture  of  the  stone 
prevents  the  hot  air  from  escaping  ;  m  con- 
sequence of  which,  it  bursts  forth  with  great 
violence,  tearing  the  stone  to  atoms,  and 
forcing  the  fragments  into  the  room. 

Probably  some  part  of  this  effect  is  due  to  the  setting  free  of  the  waier 

if  ',ryUallization~ 

158. 

Q.  When  bottled  ale  or  porter  is  set  be- 
fore a  fire,  why  is  the  cork  forced  out  some- 
times ? 

A.  Because  the  carbonic  acid  of  the  liquor 
expands  by  the  heat,  and  drives  out  the 
cork. 

Carbonic  acid  gas  is  a  compound  of  carbon  and  oxygen, 
159. 

Q.  Why  does  ale  or  porter  froth  more  af- 
ter it  has  been  set  before  the  fire  ? 

A.  Because  the  heat  of  the  fire  sets  free 
the  carbonic  acid  of  the  liquor;  which  is 
entangled  as  it  rises  through  the  liquor^ 
and  produces  bubbles  or  froth. 

160. 

Q.  When  a  boy  makes  a  balloon,  and  sets 
fire  to  the  cotton  or  sponge  (which  has  been 
flteeped  in  spirits  of  wine,)  why  is  the  bal- 
loon inflated? 

A.  Because  the  air  of  the  balloon  is  ex- 
5 


50 


CHEMICAL  ACTION. 


pan  dad  by  the  flame,  till  e  very  crumple  ifl 
inflated  and  made  smooth. 

161. 

Q.  Why  does  the  balloon  rise  after  it  haii 
been  inflated  by  the  expanded  air  ? 

A.  Because  the  same  quantity  of  air  is 
expanded  to  three  or  four  times  its  original 
volume;  and  made  somuch^^^^r,  that  even 
when  all  the  paper,  wire,  and  cotton  are 
added,  it  is  still  lighter  than  common  air. 

162. 

Q.  Why  does  smoke  rush  up  a  chimney  ? 

A.  Because  the  heat  of  the  fire  expands 
the  air  in  the  chimney ;  which  (being  thus 
made  lighter  than  the  air  fxro\mdi)  rises  up 
the  chimney,  and  carries  the  smoke  in  its 
current. 

163. 

Q.  Why  will  a  long  chimney  smoke,  un- 
less the  fire  be  pretty  fierce  ? 

A.  Because  the  heat  of  the  fire  will  not 
be  sufficient  to  rarify  all  the  air  in  the  chim^ 
my. 

164. 

Q.  Why  will  the  chimney  smoke,  unless 
the  fire  be  fierce  enough  to  heat  all  the  air 
in  the  chimney  flue  ? 


EXPANSION  OF  LIQUIDS  AND  GASES.  51 

A.  Because  the  cold  air  (condensed  in  the 
upper  part  of  the  flue)  will  sink  from  its 
own  weight;  and  sweep  the  ascending  smoke 
hack  into  the  room. 

165. 

Q.  What  is  the  use  of  a  cowl  upon  a 
chimney-pot  ? 

A,  It  acts  as  a  screen ^  to  prevent  the  wind 
from  blowing  into  the  chimney. 

166. 

Q.  What  harm  would  the  wind  do  if  it 
were  to  blow  into  a  chimney? 

A.  1st. — -It  would  prevent  the  smoke 
from  getting  out ;  and 

2nd. — The  cold  air  (introduced  into  the 
chimney  by  the  wind)  would  fall  down  the 
flue,  and  drive  the  smoke  with  it  into  the 
room. 

167. 

Q.  How  are  houses  and  other  buildings 
lieated  with  hot  air  ? 

A.  The  fire  is  kindled  in  a  grate  or  stove 
which  is  erected  in  the  cellar.  This  fire 
heats  the  air  in  contact  with  it  in  the  air 
chamber,  as  it  is  called — and  as  heated  air 
always  ascends,  it  is  forced  up  into  the  dif- 
ferent apartments  of  the  building. 


52 


(CHEMICAL  ACTION. 


160. 

Q.  What  is  fin  air  chamber  ? 

A.  It  is  an  enclosure  around  the  grate  or 
stove,  with  openings  below  to  admit  the 
cold  air  from  the  cellar  to  rush  in  to  sup- 
ply the  place  of  the  heated  air  which  as- 
cends into  the  rooms  above.  Sometimes 
the  air  chamber  is  supplied  with  cold  air 
by  pipes,  which  conduct  the  cold  air  outside 
of  the  house  into  the  air  chamber. 

169. 

Q.  Why  are  the  hricks  and  flag  stones  of 
our  pavements  frequently  loosened  after  a 
frost? 

A.  Because  the  moisture  beneath  them^ 
expanded  during  the  frost,  and  raised  the 
bricks  and  flag-stones  from  their  beds ;  but 
afterward,  the  moisture  thawed  and  con- 
densed again,  leaving  the  bricks  and  stones 
loose. 

170. 

Q.  In  England,  it  is  customary  to  place 
a  cup  in  an  inverted  position,  into  a  fruit 
pie  ;  why  is  this  done  ? 

A.  Its  principal  use  is  to  hold  the  crust  up, 
and  prevent  it  from  sinkings  when  the  cooked 
fniit  gives  way  under  it. 


EXPANSION  OF  LIQUIDS  AND  GASES.  53 


171. 

Q.  Does  not  the  cup  prevent  the  fruit  of 
(he  pie  from  boiling  over  ? 

A.  No — it  will  rather  tend  to  make  it  boil 
over,  as  there  will  be  less  room  in  the  dish. 

172. 

Q.  Explain  this. 

A.  When  the  pie  is  put  into  the  oven 
the  air  in  the  cup  will  begin  to  expand,  and 
drive  every  particle  of  juice  from  under  it; 
in  consequence  of  which,  the  pie-dish  will 
have  a  cup-full  less  room  to  hold  its  fruit  in, 
than  if  the  cup  were  taken  out, 

173. 

Q.  If  the  juice  is  driven  out  of  the  cup, 
why  is  the  cup  always  full  of  juice  when 
the  pie  is  cut  up  ? 

A.  Because  as  soon  as  the  pie  is  taken 
out  of  the  oven,  the  air  in  the  cup  begins 
to  condense  again,  'and  occupy  a  smaller  space, 
and,  as  the  cup  is  no  longer  full  of  air,  juice 
rushes  in  to  occupy  the  void. 

174. 

Q.  Why  does  juice  rush  into  the  cup 
when  the  cup  is  not  full  oi  air? 

A.  Because  tlie  external  air  presses  upon 
the  surface  of  the  juice,  which  rushes  unoh- 
'  5* 


/ 

6l  CHEMICAL  ACTION. 

strudcd  into  the  cup ;  as  mercury  risei5 
through  the  tube  of  a  barometer. 

N.  B.  Since  liie  juice  of  the  pie  runs  into  Ihe'cup,  ns  soon  as  U  is  taker 
out  of  the  oven  ;  the  cup  prevents  llie  juice  from  i»ein^r  spilt  over  the  crusty 
when  the  pie  is  carried  al)out  from  place  to  place;  although  it  does  nof 
prevent  the  fruit  from  boiling  over. 

§  II. — Expansion  of  Metals, 
175. 

Q.  What  metal  is  distinguished  from  all 
others  by  its  fluidity  at  ordinary  tempera- 
tures? 

A.  Mercury  or  quicksilver. 

176. 

Q.  Does  mercury  like  other  metals  ex 
pand  by  heat  ? 

A.  It  readily  expands  or  contracts  with 
every  variation  of  temperature. 

177. 

Q.  For  what  philosophical  instruments  is 
mercury  generally  used  ? 

A.  Its  regular  expansion  and  contraction 
by  every  increase  or  diminution  of  tempe- 
rature, renders  it  preferable  to  all  other 
liqui(is  for  filling  the  tubes  of  barometers  and 
thermometers 

178. 

Q  Why  does  the  mercury  of  a  thermth 
meter  rise  in  hot  weather  ? 


expajSSion  of  metals. 


55 


A,  Because  heat  expands  the  metd,  which 
(bemg  increased  in  bulk)  occupies  a  larger 
ftpace ;  and,  consequently,  rises  higher  ia 
the  tube. 

179. 

Q.  Why  is  a  glass  broken  when  hot  water 
is  poured  into  it  ? 

A.  Because  the  inside  of  the  glass  is  ex* 
panded  by  the  hot  water,  and  not  the  out- 
side  ;  so  the  glass  snaps ,  in  consequence  of 
this  unequal  expansion. 

180. 

Q.  Why  is  not  the  outside  of  the  glass 
expanded  by  the  hot  water  as  well  as  the 

inside  ? 

A.  Because  glass  is  a  had  conductor  of 
heat,  and  breaks  before  the  heat  of  the  inner 
surface  is  conducted  to  the  outside. 

181.  X 

Q.  Why  does  a  glass  snap  because  the 
inner  surface  is  hotter  than  the  outer  ? 

A.  Because  the  inner  surfxce  is  expanded 
and  not  the  outer ;  in  consequence  of  which, 
an  opposing  force  is  created,  which  breaks 
the  glass. 

182 

Q.  Why  is  a  china  cup  broken  if  ^tot  wa 
ter  be  poured  into  it  ? 


56 


CHEMICAL  ACTION. 


A  Because  it  is  a  had  conductor  ;  and,  a8 
the  inner  surface  expands  from  the  heat, 
(and  not  the  outer,)  an  opposing  force  is 
created,  which  breaks  the  cup. 

183. 

Q.  li  a  bar  of  metal  be  accurately  mea- 
sured when  cold ;  and  afterwards  heated 
very  hot,  will  its  dimensions  have  increased? 

A.  Yes;  all  metals  e:r/>^/i(i  by  heat ;  and 
a  bar  of  iron  when  hot  will  measure  more 
than  when  it  was  cold. 

184. 

Q.  Will  the  iron  contract  in  size  on  cool- 
ing, after  it  has  been  heated? 

A.  Yes ;  it  will  return  to  its  former 
dimensions  on  getting  cold  again. 

185. 

Q.  Why  do  most  persons  dip  their  razoi 
in  hot  loater  before  shaving  with  it? 

A.  Because  the  heat  of  the  water  ex- 
pands the  edge ;  by  that  means  rendering 
it  more  fine  and  sharp.  , 

186. 

Q.  Why  does  a  cooper  heat  his  hoops  red 
Lot  when  he  puts  them  on  a  tub? 

A  1st. — As  iron  expands  hy  heat,  the 
hoops  will  be  larger  when  they  are  red  hot ; 


EXPANSION  OF  METALS. 


57 


ill  consequence  of  which,  they  will  fit  on 
the  tub  more  easily  ;  and 

2nd. — As  iron  contracts  by  cold,  the  hoops 
will  shrink  as  they  cool  down,  and  girt  the 
tub  with  a  tighter  grasp. 

187. 

Q.  Why  does  a  wheelwright  make  the  tire 
red  hot  which  he  fixes  on  a  wheel? 

A.  1st. — That  it  may  fit  on  more  easily  ; 
and 

2nd. — That  it  may  girt  the  wheel  more 
tightly.  I- 

188. 

Q.  Why  will  the  wheelwright's  tire  fit  the 
wheel  more  easily,  for  being  made  red  hot? 

A.  Because  it  will  be  expanded  by  the 
heat ;  and  (being  larger)  will  go  on  the 
wheel  more  easily. 

189. 

Q.  Why  will  the  tire  which  has  been 
piit  on  hot,  girt  the  wheel  more  firmly? 

A.  Because  it  will  shinnk  when  it  cools 
down ;  and,  therefore,  girt  the  wheel  with  a 
tighter  grasp. 

190. 

Q.  Why  does  a  stove  make  a  crackling 
noise  when  a  fire  is  very  hot  ? 


58 


CHEMICAL  ACTION 


A.  Because  it  expands  from  the  heat  ;  and 
liie  parts  of  the  stove  rubbing  against  each 
other,  or  driving  against  the  bricks,  prod  uco 
a  crackling  noise. 

191. 

Q  Why  does  a  stove  make  a  similar  crack'^ 
hug  noise  when  a  large  fire  is  put  out  ? 

A.  Because  it  contracts  again,  when  the 
fire  is  removed ;  in  consequence  of  which, 
the  parts  rub  against  each  other  again,  and 
the  bricks  are  again  disturbed. 

192. 

Q.  Why  does  the  plaster  roui^d  a  stove 
crack  and  fall  away? 

A.  Because  (when  the  fire  is  lighted)  the 
iron -work  expands  more  than  the  brick- work 
and  plaster,  and  pushes  them  away ;  but 
(when  the  fire  is  put  out)  the  metal  shrinks 
again,  and  leaves  the  "setting''  behind. 

The  ''setting"  is  a  technical  word  for  the  plaster,  etc.,  in  immediate 
ccntnct  with  ihe  stove. 

The.=e  questions  apply  more  particularly  to  what  is  called  a  *  Franklil 
Stove  " — they  may  be  Seen  in  many  of  our  farm  houses. 

193. 

Q.  Wliy  does  the  plaster  fall  away  ? 

A.  As  a  chink  is  left  (between  the  "set* 
ting''  and  the  stove,)  the  plaster  will  fre- 
quentl}'  fall  away  from  its  own  weight. 


EXPANSION  OF  METAI^. 


59 


194. 

Q.  Wliat  other  cause  contributes  to  hnng 
the  plaster  down? 

A.  As  the  heat  of  the  fire  varies,  the  size 
of  the  iron  stove  varies  also  ;  and  this  swell- 
ing and  contracting  keep  up  such  a  constant 
disturbance  about  the  plaster,  that  it  cracks 
and  falls  off,  leaving  the  fire-place  very  un- 
sightly. 

195. 

Q.  If  the  boiler  or  kettle  attached  to  a 
kitchen  range,  be  filled  with  cold  water 
sometime  after  the  fire  has  been  lighted,  it 
will  be  very  likely  to  crack  or  burst.  Why 
is  this  ? 

A.  Because  the  heat  of  the  fire  has  caused 
the  metal  of  which  the  boiler  is  composed 
to  expand;  but  the  cold  water  very  suddenly 
contracts  again  those  parts  with  which  it 
comes  in  contact ;  and  as  one  part  is  larger 
than  the  other,  the  boiler  cracks  or  bursts. 

IDS. 

Q.  When  the  stopper  of  -decanter  ot 
smelling-bottle  sticks,  why  will  a  cloth 
wrung  out  of  hot  water,  and  wrapped  around 
the  neck  of  the  bottle,  loosen  the  stopper  ? 

A.  Because  the  hot  cloth  heats  the  neck 


60 


CHEMICAL  ACTION. 


of  the  bottle,  causing  it  to  expand^  and  con- 
sequently loosens  the  stopper. 

197. 

Q.  Why  does  the  stopper  of  a  decanter 
stick  fast  if  it  be  put  in  damp  ? 

A.  If  the  stopper  be  damj),  it  fits  the 
decanter  air-tight ;  and  if  the  decanter  was 
last  used  in  a  heated  room,  as  soon  as  the 
hot  air  enclosed  in  the  inside  has  been  con- 
densed by  the  cold,  the  weight  of  the  ex- 
ternal air  will  be  sufficient  to  press  the 
stopper  down,  and  make  it  stick  fast. 

198. 

Q.  Why  does  the  stopper  of  a  smelling- 
bottle  very  often  stick  fast  ? 

A.  Because  the  contents  of  a  smelling- 
bottle  are  very  volatile,  and  leave  the  neck 
of  the  bottle,  and  the  stopper,  damp. 

If  the  !*melling-bottle  was  last  used  in  a  hot  room,  as  soon  as  the  hot  air 
and  volatile  essence,  inside  the  bottle,  have  been  condensed  by  the  cold, 
the  weight  of  the  external  air  will  be  sufficient  to  press  the  stopper  dcw« 
and  make  it  stick. 

§  III. — Ventilation, 

199.  ^ 

Q.  What  is  ventilation  ? 
A.  The  renewal  of  fresh  air — a  continual 
ehange  of  air. 


VENTILATION. 


61 


200. 

Q.  Is  the  air  in  a  room  in  perpetual  ino* 
tion  as  the  air  abroad  is  ? 

A.  Yes;  there  are  always  .urrents  of 
air  in  the  room  we  occupy;  one  of  hot  air 
(lowing  out  of  the  room,  and  another  of  cold 
air  flowing  into  the  room. 

201. 

Q.  How  do  you  know  that  there  are  these 
two  currents  of  air  in  every  occupied  room  ? 

A.  If  I  hold  a  lighted  candle  near  the 
crevice  at  the  top  of  the  door,  the  flame  will 
be  blown  outward  (towards  the  hall ;)  but  if 
I  hold  the  candle  at  the  bottom  of  the  door, 
the  flame  will  be  blown  inwards  (into  the 
rooin.) 

N  B.  This  is  not  the  case  if  a  fire  Jje  in  the  room.  When  a  fire  i3 
lighted,  an  inward  current  is  drawn  through  all  the  crevices. 

202. 

Q.  Why  would  the  flame  be  blown  out- 
wards (towards  the  hall,)  if  a  candle  be  held 
at  the  top  of  the  door  ? 

A.  Because  the  air  of  the  room  being 
heated,  and  consequently  rarified,  ascends  ^ 
and  (floating  about  the  upper  part  of  the 
room)  some  of  it  escapes  through  the  crevice 
at  the  top  of  the  door,  producing  a  current 
of  air  outioards  (into  the  halL) 
6 


62 


CHEMICAL  ACPiON. 


203. 

Q,  Why  would  the  flame  be  blown  in* 
wards  (into  the  room,)  if  the  candle  be  held 
at  the  bottom  of  the  door  ? 

A.  Because  a  partial  vacuum  is  made  at 
the  bottom  of  the  room,  as  soon  as  the  warm 
air  of  the  room  has  ascended  to  the  ceihng, 
or  made  its  escape  from  the  room  ;  and  cold 
air  from  the  hall  rushes  under  the  door,  to 
supply  the  void. 

204. 

Q.  What  is  meant  by  a  "partial  vacuum 
being  made  at  the  bottom  of  the  room  V 

A.  A  vacuum  means  a  place  from  which 
the  air  has  been  taken;  and  a  ''partial  va- 
cuum^' means  a  place  from  which  a  part  of 
the  air  has  been  taken  away.  Thus,  when 
the  air  near  the  floor  ascends  to  the  ceiling, 
a  partial  vacuum  is  made  near  the  floor. 

205. 

Q.  And  how  is  the  vacuum  filled  up  again  ? 

A.  It  is  filled  up  by  colder  air,  which 
rushes  (under  the  door,  and  through  the 
'joindow  crevices)  into  the  room. 

206. 

Q ,  Give  me  an  illustration  ? 
A,  If  I  dip  a  pail  into  a  pond  and  fill  it 
with  water,  a  hole  (or  vacuum)  is  inade  in 


VENTILAIION. 


33 


tlie  pond  as  big  as  the  pail ;  but  the  monieut 
I  draw  the  pail  out,  the  hole  is  filled  up  by 
the  water  around. 

207. 

Q.  Show  how  this  illustration  applies  ? 

A.  The  heated  air,  which  ascends  from 
the  bottom  of  a  room,  is  as  much  taken 
away  as  the  water  in  the  pail ;  and  (as  the 
void  was  instantly  supplied  by  other  water 
in  the  pond)  so  the  void  of  air  is  supplied  by 
the  air  around. 

208. 

Q.  Why  is  a  room  (even  without  a  fire) 
generally  warmer  than  the  open  air  ? 

A.  Because  the  air  in  a  room  is  not  sub- 
ject to  much  change,  and  soon  becomes  of  the 
same  temperature  as  our  sldn,  when  it  no 
longer  feels  cold. 

209. 

Q.  Why  do  we  generally  feel  colder  out- 
of-doors  than  in-doors? 

A.  Because  the  air  (which  surrounds  ub) 
is  always  changing ;  and  as  fast  as  one  por- 
tion of  air  has  become  warmer  by  contact 
with  our  body,  another  colder  portion  sur- 
rounds us,  to  absorb  more  heat. 

210. 

Q.  Why  is  there  a  strong  draught  through 
the  keyhole  of  a  door  ? 


04 


CRj^MICAL  ACTION. 


A.  Because  the  air  in  the  room  we  occupy 
is  warmer  than  the  air  in  the  hall ;  there- 
fore, the  air  from  the  hall  rushes  through  the 
keyhole  into  the  room,  and  causes  a  draught. 

211. 

Q.  Why  is  there  a  strong  draught  under 
the  (/oor,  and  through  the  crevice  on  each 
side  ? 

A.  Because  cold  air  rushes  from  the  hall, 
to  supply  the  void  in  the  room,  caused  by 
the  escape  of  warm  air  up  the  chimney,  etc. 

212. 

Q.  "Why  is  there  always  a  draught  through 
the  window  crevices  ? 

A.  Because  the  external  air  (being  colder 
than  the  air  of  the  room  we  occupy)  rushes 
through  the  window  crevices  to  supply  the 
deficiency,  caused  by  the  escape  of  warm  air 
up  the  chimney,  etc. 

213. 

Q.  If  you  open  the  lower  sash  of  a  win- 
dow, there  is  more  draught  than  if  you  open 
the  upper  sash.    Explain  the  reason  of  this? 

A.  If  the  lower  sash  be  open,  cold  external 
air  will  rush  freely  into  the  room  and  cause 
a  great  draught  inwards ;  but  if  the  upper 
Rash  be  open,  the  heated  air  of  the  room  wDl 


VENTILATION. 


65 


msli  out,  and  (of  course)  there  will  be  less 
draught  inwards. 

214. 

Q.  By  which  means  is  a  room  better  veti" 
tilahd—By  opening  the  upper  or  the  lower 
sasli  ? 

A.  A  room  is  better  ventilated  by  opening 
(he  upper  sash  ;  because  the  hot  vitiated  air 
(which  always  ascends  toward  the  ceiling) 
can  escape  more  easily. 

215. 

Q.  l)y  which  means  is  a  hot  room  more 
quickl}'  cooled — By  opening  the  upper  or 
the  lower  sash  ? 

A.  A  hot  room  is  cooled  more  quickly  by 
opening  the  lower  sash  ;  because  the  cold  air 
can  enter  more  freely  at  the  lower  part  of 
the  room,  than  at  the  upper, 

216. 

Q.  Which  is  the  hottest  place  in  a  church, 
chapel,  or  theatre  ? 
A.  The  gallery. 

217. 

Q.  Why  is  the  gallery  of  all  public  places 
hotter  than  the  lower  parts  of  the  building  ? 

A.  Because  the  heated  air  of  the  build- 
ing ascends  ;  and  all  the  cold  air  (which  can 
enter  through  the  doors  and  windows)  keeps 
to  the  floor,  till  it  has  become  heated 
6* 


66 


CHEMICAL  ACTION. 


218. 

Q.  Why  is  the  gallenj  of  a  church  or  the- 
atre hotter  than  the  aisle  or  pit  ? 

A.  Because  the  hot  air  ascends  from  the 
bottom  to  the  top  of  the  building  ;  while  cold 
air  flows  to  the  bottom  from  the  doors  and 
windows. 

219. 

Q.  How  are  mines  ventilated  ? 

A.  The  mine  is  furnished  with  two  shafts 
or  flues.  These  flues  are  so  arranged,  that 
air  forced  down  one,  shall  traverse  the  whole 
extent  of  the  mine  before  it  escapes  by  the 
other.  By  keeping  up  a  fire  in  one  of  these 
shafts,  the  air  is  rarified  or  expanded  within, 
causing  an  ascending  current,  carrying  with 
it  all  the  noxious  gases,  and  rendering  the 
air  pure. 

220. 

Q.  What  effect  is  produced  upon  air  by 
rarif  action  ? 

A.  It  is  made  lighter  and  ascends  through 
colder  strata  ;  as  a  cork  (put  at  the  bottom 
of  a  basin  of  water)  rises  to  the  surface. 

221. 

Q.  Prove  that  rarified  air  ascends  1 
A.  When  a  boy  sets  fire  to  the  cotton  or 
gponge  of  his  balloon,  the  flame  heats  th4 


VENTILATION. 


67 


air  ;  which  becomes  so  light,  that  i{  ascends, 
and  carries  the  balloon  with  it. 

222. 

Wliy  should  stoves  be  fixed  as  neaj 
the  floor  of  a  room  as  possible  ? 

A.  In  order  that  the  air  in  the  lower  part 
of  the  room  may  be  heated  by  the  fire. 

223. 

Q.  Would  not  the  air  in  the  lower  part 
of  a  room  be  heated  equally  well  if  the 
stoves  w^ere  more  elevated  ? 

A.  No ;  the  heat  of  a  fire  has  very  little 
effect  upon  the  air  below  the  level  of  the  grate  ; 
and  therefore,  every  grate  should  be  as  near 
the  floor  as  possible. 

224. 

Q.  Our  feet  are  very  frequently  cold  when 
we  sit  close  by  a  good  fire;  Explain  the 
reason  of  this  ? 

A.  As  the  fire  consumes  the  air  which 
passes  over  it,  cold  air  rushes  through  the 
crevices  of  the  doors  and  windows,  along  the 
floor  of  the  room-,  to  supply  the  deficiency  ; 
and  these  currents  of  cold  air,  rushing  con- 
stantly over  our  feet^  deprive  thera  of  theii 
warmth. 

225 

Q.  What  is  smoke  ? 


68 


CHEMICAL  ACT! CIS. 


A.  Small  particles  of  carbon,  separated 
by  combustion  from  the  fuel,  but  not  con- 
sumed. 

226. 

Q.  Why  does  smoke  ascend  the  chimney  j 
A.  Because  the  air  of  the  room  (when  it 
passes  over  the  fire)  becomes  lighter  for  he- 
ing  heated;  (being  thus  made  lighter)  ascends 
the  chimney,  carrying  the  smoke  with  it. 

227. 

Q.  "Why  do  smoke  and  steam  curl  as  they 
ascend  ? 

A.  Because  they  are  forced  round  and 
round  by  the  ascending  and  descending  cur- 
rents of  air. 

228. 

Q.  Why  do  some  chimneys  smoke  ? 

A.  Because  fresh  air  is  not  admitted  into 
a  room  as  fast  as  it  is  consumed  by  the  fire  ; 
in  consequence  of  which  a  current  of  air 
rushes  down  the  chimney  to  supply  the  defir 
ciency,  driving  the  smoke  along  wdth  it. 

229. 

Q.  AVliy  cannot  air  be  supplied  as  fast  as 
it  is  consumed  by  the  fire  ? 

A.  Curtains  round  the  windows,  sand 
bags  at  the  threshold  of  the  doors,  and  all 
such  contrivances  keep  out  the  draught. 


VENTILATIOxN. 


G9 


230. 

Q,  Why  will  the  air  come  down  the 
tkimmy  ? 

A.  Because  it  can  get  into  the  room  in 
no  other  way,  if  the  doors  and  windows  are 
all  made  air-tight. 

231. 

Q.  What  is  the  best  remedy  in  such  a 
case  ? 

A.  The  speediest  remedy  is  to  open  the 
door  or  window ;  but  by  far  the  best  re- 
medy, is  to  carry  a  small  tube  from  the 
hearth  into  the  external  air. 

232. 

Q.  Why  is  that  the  best  remedy? 

A.  Because  the  fire  will  be  plentifully 
supplied  with  air  by  the  tube ;  the  doors 
and  windows  may  all  remain  air-tight ;  and 
we  may  enjoy  a  warm  fire-side,  without  the 
inconvenience  of  draughts  of  air  and  cold 
feet. 

233. 

Q.  Why  is  a  chimney  raised  so  high  above 
the  roof? 

A.  That  it  may  not  smoke;  as  all  funnels 
do  which  are  too  short 

234. 

Q.  What  is  meant  by  the /?m7ir/ or  flu. 
of  a  chimney  ? 


70 


CHEMICAL  ACTION. 


A.  That  part  of  a  chimney  through  which 
the  smoke  passes. 

235. 

Q.  Why  does  a  chimney  smoke  if  fun- 
nel be  very  short  ? 

A.  Because  the  draught  of  a  short  flue  is 
too  slack  to  carry  the  smoke  up  the  chimneyo 

236. 

Q.  Why  is  the  draught  of  a  short  flue 
more  slack  than  that  of  a  long  one  ? 

A.  1st. — Because  the  fire  is  always  dull 
and  sluggish  if  the  chimney  be  too  short : 

2nd. — Because  the  smoke  rolls  out  of  the 
chimney  before  it  has  acquired  its  full  ve- 
locity ;  and, 

3d. — ^Because  the  wind,  rain,  and  air, 
have  more  influence  over  a  short  funnel 
than  over  a  long  one. 

237. 

Q.  Why  is  the  fire  alw^ays  dull  and  slug-^ 
gish,  if  the  chimney  flue  be  very  short  ? 

A.  Because  the  draught  is  bad ;  and,  aa 
the  rarified  air  passes  very  tardily  up  the 
chimney — fresh  air  flows  as  tardily  toward 
the  fire ^  to  supply  it  with  oxygen. 

238. 

Q.  Why  does  not  smoke  acquire  its  full 
velocity  in  a  short  funnel  ? 


VENTILATION. 


71 


A.  Because  the  higher  smoke  ascends, 
(pro voided,  the  fire  be  clear  and  hot  and  the 
flue  be  unobstructed)  the  faster  it  goes ;  if, 
therefore,  a  funnel  he  very  short,  the  smoke 
never  acquires  its  full  velocity. 

239. 

Q.  Does  the  draught  of  a  chimney  de- 
pend on  the  speed  of  the  smoke  through  the 
flue? 

A.  Yes.  The  more  quickly  hot  air  flies 
up  the  chimney,  the  more  quickly  cold  air 
will  rush  toward  the  fire  to  supply  the  place; 
and  therefore,  the  longer  the  flue,  the  greater 
the  draught. 

240. 

Q.  Why  are  the  chimneys  of  manufacto- 
ries made  so  very  long  ? 

A.  To  increase  the  intensity  of  the  fire. 

241. 

Q.  Why  is  the  intensity  of  a  fire  increased 
by  lengthening  the  flue  ? 

A.  Because  the  draught  being  greater, 
more  fuel  is  consumed  in  the  same  time ; 
and,  of  course,  the  intensity  of  the  heat  isf 
proportionally  greater. 

242. 

Q,  If  a  short  chimney  cannot  be  length 


72 


CHEMICAL  ACTION. 


ened,  what  is  the  best  remedy  to  prevent 
smoking  ? 

A.  To  contract  the  opening  of  the  chimney 
contiguous  to  the  stove. 

243. 

Q.  Why  will  a  smaller  opening  in  that 
part  of  the  chimney  near  the  ^re  prevent 

smoJdng  ? 

A.  Because  the  air  will  be  compelled  to 
pass  nearer  the  fire  ;  and  (being  more  heated) 
will  rise  through  the  chimney  more  rajDidly ; 
this  increase  of  heat  will,  therefore,  compen- 
sate for  the  shortness  of  the  flue. 

244. 

Q.  Why  will  a  room  be  full  of  smoke  if 
there  be  two  fires  in  it  ? 

A.  Because  the  fiercer  fire  will  exhaust 
the  most  air ;  and  draw  from  the  smaller 
one,  to  supply  its  demand. 

245. 

Q.  Why  will  a  chimney  smoke  if  there  be 
a  fire  in  two  rooms  communicating  with  each 
other  ? 

A.  Because  (whenever  the  door  between 
the  two  rooms  is  opened)  air  will  rush  from 
the  chimney  of  the  inferior  fire  to  supply 
the  other  ;  and  both  rooms  will  be  filled  with 
«moke. 


VENTILATION. 


73 


246. 

Q.  What  is  the  best  remedy  in  this  case? 

A.  Let  a  tube  be  carried  from  the  hearth 
ctf  each  fire  into  the  external  air;  and  then 
ea:h  fire  will  be  so  well  supplied,  that 
neither  will  need  to  borrow  from  the  other. 

247. 

Q.  Why  do  vestry  chimneys  so  ofteu 
smoke  ? 

A.  Because  the  wind  (striking  against 
the  steeple)  is  reflected  hack,  and,  rushing 
down  the  vestry  chimney,  forces  the  smoke 
tnto  the  room. 

243. 

Q.  Why  does  a  house  in  a  valley  very 
often  smoke  ? 

A.  Because  the  wind  (striking  against 
the  surrounding  hills)  hounds  hack  again  upon 
the  chimney,  and  destroys  its  draught. 

249. 

Q.  What  is  the  common  remedy  in  this 
case? 

A.  To  fix  a  cowl  on  the  chimney  top  to 
turn  like  a  weather-cock,  and  present  its 
back  to  the  wind. 

250. 

Q.  Why  will  not  a  cowl  always  prevent  a 

chimney  smoking  ? 
7 


74 


CHEMICAL  ACTION. 


A.  Because  if  the  wind  be  strong,  and 
there  should  be  a  steeple  or  hill  near  the 
chimney,  it  would  keep  the  opening  of  the 
coidI  towards  the  steeple  or  hill;  and  then  tlie 
reflected  wind  would  Uoiu  into  the  coivl,  and 
down  the  chimney. 

251. 

Q:  As  a  cowl  is  not  a  perfect  remedy,  can 
any  other  be  suggested  ? 

A.  Yes.  If  the  chimney-flue  can  be 
carried  higher  than  the  steeple  or  hill,  no 
wind  can  enter  the  flue. 

252. 

Q.  If  a  chimney  flue  be  carried  up  higher 
than  the  steeple  or  hill,  why  cannot  the 
wind  enter  it  ? 

A.  Because  the  reflected  wind  would 
strike  against  the  sides  of  the  chimney- 
flue,  and  not  pass  over  the  opening  at  all. 

253. 

Q.  In  what  other  cases  will  a  chimney 
smoke  ? 

A.  If  the  door  and  fire-place  are  both  on 
the  same  side  of  the  room,  the  chimney  will 
very  often  smoke. 

254. 

Q.  Why  will  a  chimney  smoke  if  the  door 
md  fire-place  are  both  on  the  same  side  ? 


VENTILATION. 


A.  Because  (whenever  the  door  is  open- 
ed) a  current  of  air  will  blow  obliquely  into 
the  chimneTj  place,  and  drive  the  smoke  into 
the  room. 

255. 

Q.  What  remedy  can  be  applied  to  this 
evil  ? 

A.  The  door  must  be  set  opposite  to  the 
chimney-place,  or  nearly  so ;  and  then  the 
draught  from  the  door  will  blow  the  smoke  up 
the  chimney,  and  not  into  the  room. 

256. 

Q,  Why  will  a  chimney  smoke  if  it  needs 
sweeping!, 

A.  Because  loose  soot  obstructs  the  free 
passage  of  the  smoke,  delays  its  current ,  and 
prevents  the  draught. 

257. 

Q.  Why  will  a  chimney  smoke  if  it  be  out 
of  repair? 

A.  1st. — Because  the  loose  mortar  and 
]>ricks  obstruct  the  smoke;  and 

2nd. — 'Cold  air  (oozing  through  the 
chinks)  chills  the  air  in  the  chimney,  and  pre- 
vents its  ascent. 

258. 

Q.  Why  does  an  old  fashioned  farm-hmise 
rhimney  often  smoke  ? 


76 


CHEMICAL  ACTION. 


A.  Because  the  opening  of  the  chimney- 
place  is  so  very  large,  that  much  of  the  aii 
which  goes  up  the  chimney,  has  never 
passed  near  enough  to  the  fire  to  become  heated; 
and  this  cold  air  (mixing  with  the  hot)  so 
reduces  the  temperature  of  the  air  in  the 
chimney,  that  it  ascends  very  slowly  and 
the  draught  is  destroyed. 

259 

Q.  Why  does  a  chimney  smoke  if  the 
draught  be  slack  ? 

A.  Because  the  current  of  air  up  the 
chimney  is  not  powerful  enough  to  huoy  up 
the  smoke  through  the  flue. 

260. 

Q.  If  the  opening  of  a  chimney  be  too 
large  what  remedy  can  be  applied  ? 

A.  The  chimney-place  must  be  contracted. 

261. 

Q.  Why  w^ill  contracting  the  chimney- 
place  prevent  its  smoking  ? 

A.  Because  the  air  will  then  pass  nearer 
the  fire;  and  (being  more  heated)  will  fly 
faster  up  the  chimney. 

262. 

Q.  Wliy  do  almost  all  chimneys  smoke 
in  gusty  weather  ? 

A.  Because  the  column  of  smoke  is  sud- 


VENTILATION. 


77 


denly  chilled  by  the  wind,  and  (being  un- 
able to  ascend)  rushes  back  into  the  room. 

263 

Q  What  is  the  use  of  a  chimney -pot  ? 
A,  It  serves  to  increase  the  draught  when 
the  opening  of  a  chimney  is  too  large. 

264. 

Q.  How  does  a  chimney-pot  increase  the 
draught  of  a  chimney  ? 

A.  As  the  same  quantity  of  hot  air  has  to 
escape  through  a  smaller  openings  it  must 
pass  through  more  quickly. 

265. 

Q.  Why  do  blowers^  when  placed  before  a 
grate,  tend  to  kindle  the  fire  ? 

A.  Because  the  air  (by  passing  through 
the  fire)  is  made. much  hotter,  and  ascends 
the  chimney  more  rapidly. 

266. 

Q.  Why  is  a  fire  better  supplied  with 
oxygen  while  the  blower  is  before  it  ? 

A.  Because  the  blower  increases  the 
draught ;  and  the  faster  the  hot  air  flies  up' 
the  chimney,  the  faster  will  cold  air  rush 
towards  the  fire,  to  supply  it  with  oxygen 

267. 

Q.  Why  does  a  parlor  often  smell  dis- 
agreeably of  soot  in  summer  time  ? 


78 


CHEMICAL  ACTION. 


A.  Because  the  air  in  tlie  chimney  (being 
colder  than  the  air  in  the  jxrrlor)  descends 
into  the  room,  and  leaves  a  .^eeable  smell 
of  soot  behind. 

268. 

Q.  Why  does  a  poker  tail  uc,  oss  a  dull  jin 
evive  it  ? 

A.  For  two  reasons  :  1  .d, — Because  the 
poker  concentrates  the  heat,  and  therefore  in- 
creases it ;  and 

2nd. — Air  is  arrested  in  the  narrow  aper- 
ture between  the  poker  and  the  coals,  and 
a  draught  created. 

269. 

Q.  Why  are  fires  placed  on  the  floor  of  a 
room,  and  not  tovv^ards  the  ceiling  ? 

A.  Because  heated  air  always  ascends. 
If,  therefore,  the  fire  were  not  near  the  floor, 
the  air  of  the  lower  part  of  the  room  would 
never  be  heated  by  the  fire  at  all. 

270. 

Q.  If  you  take  a  poker  out  of  the  fire,  and 
hold  the  hot  end  downwards,  why  is  the  handle 
intensely  hot  ? 

A.  Because  the  hot  end  of  the  poker  heats 
the  air  around  it ;  and  this  hot  air  (in  its 
ascent)  scorches  ih(i  poker  and  the  hand  whi'^li 
holds  it. 


CONDUCTION  OF  HEAT. 


79 


271. 

Q.  How  should  a  red  hot  poker  be  carried, 
R)  as  not  to  hum  our  fingers  ? 

A.  With  the  hot  end  upwards ;  for  then 
the  air  (heated  by  the  poker)  would  not 
paes  over  our  hand  and  scorch  it. 

SECTION  II.  CONDUCTION  OF  HEAT. 

272. 

Q.  What  is  meant  by  conduction  of  heat  ? 
A.  Heat  communicated  from  one  body  to 
another  by  actucd  contact. 

§  I. — Conductors  of  Heat 
273. 

Q.  Why  do  some  things  feel  colder  than 
others  ? 

A.  Principally  because  they  are  better  c  on- 
ductors ;  and  draw  off  heat  from  our  body 
much  faster. 

274 

Q.  What  are  the  best  conductors  of  heat  ? 
A.  Dense,  solid  bodies,  such  as  metal  and 
Btone. 

275. 

Q.  "Which  metals  are  the  most  rapid  con* 
ductors  of  heat  ? 


80 


CHEMICAL  ACTION. 


A.  The  best  conductors  of  heat  arf;  1 
gold ;  2,  silver ;  3,  copper  : 

The  next  best  are  4,  platinum;  5,  iron; 
6,  zinc;  7,  tin.    Lead  is  a  very  inferior  con 
ihicter  to  any  of  the  preceding  metals. 

276. 

Q.  What  are  the  worst  conductors  of  heat? 
A   All  light  and  porous  bodies;  such  as 
hair,  fur,  wool,  charcoal,  and  so  on. 

Two  of  the  worst  conductors  known  are  hare's  fur  and  eider  down  ; — tha 
two  next  worst  are  beaver's  fur  and  raw  siik  ; — then  wood  and  luinp- 
blaok  ; — then  cotton  and  fine  lint ; — then  charcoal,  wood  ashes,  &c. 

277 

Q.  Why  does  a  piece  of  wood  (blazing  at 
one  end)  not  feel  hot  at  the  other? 

A.  Because  wood  is  so  bad  a  conductor,  that 
heat  does  not  traverse  freely  through  it; 
hence,  though  one  end  of  a  stick  be  blaz- 
mi  the  other  end  may  be  quite  cold. 

273. 

Q.  Why  does  hot  metal  feel  more  intensely 
xuarm  than  hot  wool  ? 

A.  Because  metal  gives  out  a  much 
greater  quantity  of  heat  in  the  same  space  of 
time;  and  the  influx  of  heat  is,  consequently, 
more  perceptible. 

279. 

Q.  Why  does  money  in  our  pocket  fe^l 
very  hot  when  we  stand  before  a  fj'e? 


CONDUCTORS  OF  HEAT. 


81 


A.  Beca^ise  metal  is  an  excellent  conduc- 
tor, and  becomes  rapidly  heated.  For  the 
Bame  reason,  it  becomes  rapidly  cold,  when- 
ever it  comes  in  contact  with  a  body  coldc? 
than  itself, 

280. 

Q.  Why  does  a  poker  (resting  on  a  fea 
der)  feel  colder  than  the  hearth-rug,  which  is 
further  off  the  fire  ? 

A.  Because  the  poker  is  an  excellent  con- 
ductor, and  draws  heat  from  the  hand  much 
more  rapidly  than  the  woolen  hearth-rug^ 
which  is  a  very  bad  conductor :  though  both, 
therefore,  are  equally  warniy  the  poker  seems 
to  be  the  colder. 

281, 

Q.  Why  does  an  iron  pump-handle  feel  in- 
tensely cold  in  winter? 

A.  Because  it  is  an  excellent  conductor, 
and  draws  off  the  heat  of  our  hand  so  ra- 
pidly, that  the  sudden  loss  produces  a  sen- 
sation of  intense  coldness. 

232. 

Q.  Is  the  ivon  handle  of  the  pump  really 
tolder  than  the  wooden  j^mj?  itself? 

A.  No ;  every  inanimate  substance  (ex 
posed  to  the  same  temperature)  possesses 
in  reality  the  same  degree  of  heat. 


82 


CHEMICAL  ACTION. 


233. 

Q.  Why  does  the  iron  handle  seem  so 
much  colder  than  the  wooden  j)ump? 

A.  Merely  because  the  iron  is  a  better  con- 
ductor; and,  therefore,  draws  off  the  heat 
from  our  hand  more  rapidly  than  wood 
:loes. 

284. 

Q.  Why  does  a  stone  or  marble  hearth  feel 
to  the  feet  colder  than  a  carpet  or  hearth- 
rug ? 

A.  Because  stone  and  marble  are  good  con- 
ductors ;  but  woolen  carpets  and  hearth -rugs 
are  very  bad  conductors. 

285. 

Q.  How  does  the  stone  hearth  make  our 
feet  cold  ? 

A.  As  soon  as  the  hearth-stone  has  ab- 
sorbed a  portion  of  heat  from  our  foot,  it 
instantly  disposes  of  it,  and  calls  for  a  fies'h 
supply;  till  the  hearth-stone  has  become  of 
the  sa?ne  temperature  as  the  foot  placed  upon  ii 

286. 

Q.  Do  not  also  the  woolen  carpet  and 
hearth-rug  conduct  heat  from  the  human 
body? 

A.  Yes ;  but  being  very  bad  conductors, 
thej^  convey  the  heat  away  so  slowly^  that 
tlie  loss  is  scarcely  perceptible. 


CONDUCTORS  OF  HEAT. 


83 


287. 

Q.  Is  the  cold  hearth-stone  in  reality  of 
the  same  temperature  as  the  warm  carpet  ? 

A.  Yes;  every  thing  in  the  room  is 
really  of  one  temperature;  but  some  things 
feel  colder  than  others,  because  they  are 
better  conductors. 

288. 

Q.  How  long  will  the  hearth-stone  feel 
cold  to  the  feet  resting  on  it  ? 

A.  Till  the  feet  and  the  hearth-stone  are 
both  of  the  same  temperature ;  and  then  the 
sensation  of  cold  in  the  hearth-stone  will 
go  off. 

289. 

Q.  Why  would  not  the  hearth-stone  feel 
cold,  when  it  is  of  the  same  temperature  as 
our  feet? 

A.  Because  the  heat  would  no  longer 
rush  out  of  our  feet  into  the  hearth-stone,  in 
s^rder  to  produce  equilibrium. 

290. 

Q  Why  does  the  hearth-stone  (when  the 
jfiie  is  lighted)  feel  hotter  than  the  hearth- 
rug  ? 

A.  Because  the  hearth-stone  is  an  excel- 
lent conductor,  and  parts  with  its  heat  very 
readily;  but  the  woollen  hearth-rug  (beiDi^ 


84 


CHEMICAL  ACTION. 


a  had  conductor)  parts  with  its  heat  very 
reluctantly. 

291. 

Q.  Why  does  parting  with  heat  rapidly 
inake  the  hearth-stone  feel  warm  ? 

A .  Because  the  rapid  influx  of  heat  raises 
the  temperature  of  our  body  so  suddenly^ 
that  we  cannot  help  perceiving  the  increase. 

292. 

Q.  Why  does  the  non-conducting  power 
of  the  hearth-rug  prevent  its  feeling  so  hot 
as  it  really  is  ? 

A.  Because  it  parts  with  its  heat  so  slowly 
and  gradually,  that  we  scarcely  perceive  its 
transmission  into  our  feet. 

293. 

Q.  Why  are  cooking  vessels  often  furnished 
with  wooden  handles  ? 

A.  Because  wood  is  not  a  good  conductor, 
like  metal ;  and,  therefore,  wooden  handles 
prevent  the  heat  of  the  vessel  from  rushing 
into  our  hands,  to  burn  them. 

294. 

Q.  Why  is  the  handle  of  a  metal  tea-pot 
made  of  wood  ? 

A.  Because  ivood  is  a  had  conductor;  there- 
fore, the  heat  of  the  boiling  water  is  not  so 


CONDUCTORS  OF  HEAT. 


85 


quickly  conveyed  to  our  hand  by  a  wooden 
handle,  as  by  one  made  of  metal. 

295. 

Q.  Why  would  a  metal  handle  hum  the 
hand  of  the  tea-maker  ? 

A.  Because  metal  is  an  excellent  conduc-^ 
tor;  therefore,  the  heat  of  boiling  water 
would  rush  so  quickly  into  the  metal  handle, 
that  it  would  burn  our  hand. 

296. 

Q  Prove  that  a  metal  handle  would  be 
hotter  than  a  loooden  one. 

A.  If  w^e  touch  that  portion  of  the  metal, 
into  which  the  wooden  handle  is  fixed,  we 
shall  find  that  the  wooden  handle  feels  cold, 
but  the  metal  intensely  hot. 

297. 

Q.  When  we  plunge  our  hands  into  a 
basin  of  water,  why  does  it  produce  a  sensa- 
tion of  cold  ? 

A.  Because  water  is  a  better  conductor  than 
air ;  and,  as  it  draws  off  the  heat  from  oui: 
hands  more  rapidly,  it  feels  colder. 

298. 

Q.  Why  does  the  conducting  power  of 
water  make  it  feel  colder  than  air  ? 

A.  Because  it  abstracts  heat  from  our  hands 
so  rapidly,  that  we  feel  its  loss  ;  but  the  air 
8 


86  CHEMICAL  ACTION. 

abstracts  heat  so  very  slowly,  that  its  gradvd 
loss  is  hardly  perceptible. 

299. 

Q.  Is  water  a  good  conductor  of  heat  ? 

A.  No ;  no  liquid  is  a  good  conductor  c  f 
heat;  but  yet  water  is  a  much  better  con 
duct  or  than  air. 

300. 

Q.  Why  is  water  a  better  conductor  of  heat 
than  air  ? 

A.  Because  it  is  less  subtile  ;  and  the  con- 
ducting power  of  any  substance  depends 
upon  its  solidity,  or  the  closeness  of  its  par- 
ticles. 

301. 

Q.  How  do  you  know  that  water  is  not  a 
good  conductor  of  heat  ? 

A.  Because  it  may  be  made  to  boil  at  its 
surface,  without  imparting  sufficient  heat  to 
mdt  ice  a  quarter  of  an  inch  below  the  surface. 

302. 

Q.  Why  are  not  liquids  good  conductors  of 
heat? 

A,  Because  the  heat  (which  sliould  be 
transmitted)  produces  evaporation,  and  flies 
off  in  the  vapor. 

303. 

Q.  Why  are  hot  bricks  (wrapped  hi  cloth) 


CONDUCTORS  OF  HEAT. 


87 


employed  in  cold  weather  to  keep  tlie  fett 
jvarin  ? 

A  Because  bricks  are  had  conductors  of 
heat,  and  cloth  or  ^dimi^X  still  worse  ;  m  con- 
sequence of  which,  a  hot  brick  (wrapped  in 
flannel)  will  retain  its  heat  a  very  long  time. 

304. 

Q  Is  air  a  good  conductor  ? 
A.  No ;  air  is  a  very  had  conductor  ;  and 
IS  heated  (like  water)  by  convection, 

305. 

Q.  How  is  a  room  warmed  by  a  stove  ? 

A.  The  air  nearest  the  fire  is  made  hot 
first  and  rises ;  cold  air  then  descends,  is 
heated,  and  ascends  in  like  manner;  and 
this  interchange  goes  on  till  all  the  air  ol' 
the  room  is  warmed. 

306. 

Q.  If  air  be  a  had  conducto?  of  heat,  whj/ 
should  we  not  feel  as  warm  witliout  clothing, 
as  when  we  are  wrapped  in  wool  and  fur  1 

A.  Because  the  air  (which  is  cooler  than 
our  body)  is  never  at  rest ;  and  every  fresh 
particle  of  air  draws  off  a  fresh  portion  of 
heat. 

307, 

Q.  ^Vhy  are  woolens  and  furs  used  for 
dothing  in  cold  weather  ? 


88 


CHEMICAL  ACTION. 


A.  Because  they  are  very  had  conductor!^ 
of  lieat ;  and,  therefore,  prevent  the  loarmth 
of  the  hcdy  from  being  drawn  off  hj  the  c(M 
air. 

308. 

Q.  Do  not  AYOolens  and  furs  actually  r^- 
part  heat  to  the  body  ? 

A.  No ;  they  merely  prevent  the  heat  of 
the  body  from  escaping. 

309. 

Q.  Where  would  the  heat  escape  to,  if 
the  body  were  not  wraj^ped  in  wool  or  fur  ? 

A.  The  heat  of  the  body  would  fly  off 
into  the  air ;  for  the  cold  air  (coming  in 
contact  with  our  body)  would  gradually 
draw  away  its  heaty  till  it  was  as  cold  as  the 
air  itself. 

310 

Q.  "What  then  is  the  principal  use  of  cloth- 
mg  in  winter  time  ? 

A.  1st. — To  prevent  the  animal  heat 
from  escaping  too  freely ;  and 

2nd. — To  protect  the  body  from  the  eX" 
ternal  air  (or  wind,)  which  would  carry 
away  its  heat  too  rapidly. 

311. 

Q  Why  are  beasts  covered  with  fuTy  hair 
or  wool? 


CONDUCTORS  OF  HEAT. 


89 


A.  Because  fur,  hair  and  wool,  are  very 
^low  conductors  of  heat;  and  (as  dumb  ani- 
mals cannot  be  clad,  like  human  beings) 
God  has  given  them  a  robe  of  hair  or  vjool, 
to  keep  them  tvarm. 

312. 

Q  Why  are  birds  covered  v/ith  down  or 
feathers  ? 

A.  Because  down  and  feathers  are  very 
had  conductors  of  heat ;  and  (as  birds  cannot 
be  clad,  like  human  beings)  God  has  given 
them    robe  of  feathers,  to  keep  them  warm. 

313 

Q.  Why  are  wool,  fur,  hair  and  feathers^ 
such  slow  conductors  of  heat  ? 

A.  Because  a  great  quantity  of  air  lurks 
entangled  between  the  fibres ;  and  air  is  a 
very  bad  conductor  of  heat. 

The  warmest  clothincr  is  thai  which  fits  the  body  rather  loosely  ;  because 
more  hot  air  will  be  confined  by  a  moderately  loose  garment  than  by  one 
which  fils  the  body  tightly. 

314. 

Q.  Why  is  moderately  loose  clothing 
warmt  ^  than  that  which  fits  tightly  ? 

A.  Because  air  is  a  bad  conductor ;  and 
the  qumtity  of  air  confined  between  our 
bodies  and  clothing — prevents ; 

Isf.- -The^  heat  of  our  bodies  from  esrof- 
ing ;  and 

8* 


90 


CHEMICAL  ACTION. 


2nd. — The  external  air  from  coming  into 
contact  with  om-  bodies.  But  if  our  cloth 
hig  is  sufficiently  loose  to  admit  of  a  free 
drculatioii  of  air,  we  shall  feel  cold  ;  and  on 
the  contrary  if  it  fits  very  tightly  it  impedes 
tlie  free  circulation  of  the  blood  and  we 
feel  cold. 

315. 

Q.  Does  not  the  bad  conducting  power 
of  air  enable  persons  to  judge  whether  an 
egg  be  new  or  stale  ? 

A.  Yes ;  touch  the  larger  end  of  the 
shell  with  your  tongue ;  if  it  feels  warm^ 
the  egg  is  stale  ;  if  not^  it  is  new-laid. 

316. 

Q.  Why  will  the  shell  of  a  stale  egg  feel 
■warm  to  the  tongue  ? 

A.  Because  the  thick  end  of  an  egg  con- 
tains a  small  quantity  of  air  (between  the 
shell  and  the  white;)  when  the  egg  is  stale 
the  white  shrinks,  and  the  confined  air  ac- 
cordingly expands. 

317. 

Q.  Why  do  we  feel  colder  in  windy  wea- 
ther than  in  a  calm  day  ? 

A.  Because  the  j)articles  of  air  pass  over 
us  more  rapidly;  and  every  fj-esh  ])article 
t^akes  from  us  some  portion  of  heat. 


CONDUCTORS  OiP  flEAT.  91 
318. 

Q.  Show  the  wisdom  of  God  in  making 
the  air  a  bad  conductor  ? 

A.  If  air  were  a  good  «  onductor  [like  iron 
ftnd  stone)  heat  Avould  be  drawn  sc  rapidly 
from  our  body,  that  we  should  be  chilled  ta 
death.  Similar  evils  would  be  felt  also  l>y 
all  the  animal  and  vegetable  world. 

319. 

Q.  Why  are  rooms  much  warmer,  for  Ix!;- 
ing  furnished  with  double  doors  and  loin- 
doios  ? 

A.  Because  air  is  a  bad  conductor ;  and 
the  air  confined  between  the  double  door?" 
and  windows,  opposes  both  the  escape  of 
warm  air  out  of  the  room,  and  of  cold  aii 
into  the  room. 

320. 

Q.  Why  is  a  room  warmer  when  the  wm- 
dow  curtains  are  drawn  or  the  shutters  shut  ? 

A.  Because  air  is  a  bad  conductor  ;  and 
the  air  confined  between  the  curtains  or 
shutters  and  the  window,  opposes  both  the 
escape  of  warm  air  out  of  the  room,  and  of 
cold  air  into  it. 

321. 

Q.  Why  does  linen  shirt  feel  colder  than 
ft  cotton  one  ? 


92 


CHEMICAL  ACTION. 


A.  Because  linen  is  a  much  better  condut- 
tor  than  cotton ;  and,  therefore,  (as  soon  as 
it  touches  the  bod 7)  it  draws  away  the  heat 
more  rapidly,  and  produces  a  greater  sensa- 
tion of  cold, 

322. 

Q.  Why  is  the  face  cooled  hy  wiping  the 
temples  with  a  fine  cambric  handkerchief? 

A.  Because  the  fine  fibres  of  the  cam- 
bric have  a  strong  capillar?/  attraction  for 
moisture,  and  are  excellent  conductors  of  heat: 
in  consequence  of  which,  the  moisture  and 
heat  are  abstracted  from  the  face  by  the  cam- 
bric, and  a  sensation  of  coohiess  produced. 

"  Capillary  attraction,"  i.  e.  the  attraction  of  a  thread  or  hair.  Thti 
wick  of  a  candle  is  wet  with  grease,  because  the  melted  tallow  runs  up 
die  cotton  from  capillary  attraction. 

323. 

Q.  Why  would  not  a  cotton  handkerchief 
do  as  well  ? 

A.  Because  the  coarse  fibres  of  cotton 
Iiave  very  little  capillary  attraction,  and 
are  very  bad  conductors  ;  in  consequence  of 
which,  the  heat  of  the  face  would  be  in- 
creased (rather  than  diminished)  by  the  u&'e 
of  a  cotton  handkerchief. 

324. 

Q.  Is  the  earth  a  good  conductor  of  heat? 
A.  No ;  the  earth  is  a  very  bad  conduc- 
tor of  heat. 


CONDUCTORS  OF  HEAT. 


93 


325. 

Q.  Wliy  is  the  earth  a  had  conductor  of 
heat  ? 

A.  Because  its  particles  are  not  contma^ 
^us  ;  and  the  power  of  conducting  heat  le 
pends  upon  the  continuity  oj  matter . 

326. 

Q.  Why  is  the  earth  {below  the  surface) 
warmer  in  winter  than  the  surface  itself? 

A.  Because  the  earth  is  a  had  conductor 
of  heat;  and,  therefore,  (although  the 
ground  be  frozen,)  the  frost  never  pene- 
trates more  than  a  few  inches  helow  the  sur- 
face. 

327. 

Q.  Why  is  the  earth  (below  the  surface) 
cooler  in  summer  than  the  surface  itself? 

A.  Because  the  earth  is  a  had  conductor 
of  heat ;  and,  therefore,  (although  the  sur 
face  he  scorched  with  the  burning  sun,)  the 
intense  heat  cannot  penetrate  to  the  loots 
of  the  plants  and  trees. 

328. 

Show  the  wisdom  of  God  in  making  the 
earth  a  had  conductor  ? 

A.  If  the  heat  and  cold  coidd  penetrate  the 
earth  (as  freely  as  the  heat  of  a  fire  pene- 
trates iron,)  the  springs  would  be  dried  up 


94 


CHEmCAL  ACTION. 


in  summer,  and  frozen  in  winter ;  and  all 
vegetation  would  perish. 

329. 

Q.  Why  does  the  Bible  say,  that  God 
^•^giveth  snow  like  wool?'' 

A.  Because  snow  (being  a  very  had  con* 
duct  or  of  heat)  protects  vegetables  and  seeds 
from  the  frost  and  cold. 

330. 

Q.  How  does  the  non-conducting  joower 
of  snow  protect  vegetables  from  the  frost  and 
cold? 

A.  It  prevents  the  heat  of  the  earth  from 
being  drawn  off  by  the  cold  air  which  rests 
upon  it. 

331. 

Q.  Why  is  water  from  a  spring  always 
cool,  even  in  summer  1 

A.  Because  the  earth  is  so  had  a  conductor, 
that  the  burning  rays  of  the  sun  can  pene- 
trate only  a  few  inches  below  the  surface ; 
in  consequence  of  which,  the  springs  of  wa- 
ter are  not  affected  by  the  heat  of  sunimer 

332 

Q.  Why  is  it  cool  under  a  shady  tree  in  a 
hot  summer's  day  ? 

A.  1st, — Because  the  overhanging  fo- 
liage screens  off  the  rays  of  the  sun  ; 


CONDUCTORS  OF  HEAT. 


95 


2nd. — As  the  rays  of  the  sun  are  warded 
ofi',  the  air  (beneath  the  tree)  is  not  heated 
by  the  reflection  of  the  earth  ;  and 

3rd. — The  leaves  of  the  trees,  bemg  non- 
conductors, allow  no  heat  to  penetrate  them 

333. 

Q.  Why  do  persons  use  paper  or  woolen 
kettle-holders  ? 

A.  Because  paper  and  woolen  are  both 
very  had  conductors  of  heat ;  in  consequence 
of  which,  the  heat  of  the  kettle  does  not 
readily  pass  through  them  to  the  hand. 

334. 

Q.  Does  the  heat  of  the  boiling  kettle 
fiever  get  through  the  woolen  or  paper  kettle- 
holder  ? 

A.  Yes;  but  though  the  kettle-holder  be- 
came as  hot  as  the  kettle  itself,  it  would 
neyev  feel  so  hot. 

335. 

Q.  Why  w^ould  not  the  kettle-holder  fed 
so  hot  as  the  kettle,  when  both  are  of  the 
same  temperature  ? 

A.  Because  it  is  a  very  bad  conductor, 
and  disposes  of  its  heat  too  slowly  to  be  per- 
reptible  ;  but  metal  (being  an  excellent  con- 
ductor) disposes  of  its  heat  so  quickly,  that 
the  sudden  influx  is  pauiful. 


90 


CHEMIC.VL  ACTION. 


336. 

Q  Why  is  the  bottom  of  a  kettle  nearly 
cold  when  the  water  is  boiling  hot  ? 

A.  Because  black  soot  is  a  very  bad  con- 
du  dor  of  heat ;  and,  therefore,  the  heat  of 
thj  boiling  water  takes  some  time  before  it 
gets  through  the  soot  which  adheres  to  the 
bottom  of  the  kettle. 

337. 

Q.  Why  is  the  lid  of  a  kettle  intensely  hot 
when  the  water  boils  ? 

A.  Because  the  bright  metal  lid  is  an 
admirable  conductor  ;  and,  therefore,  the  heat 
from  the  boiling  water  pours  into  our  hand  the 
moment  we  touch  it. 

338. 

Q.  Why  are  ice-houses  lined  with  strata , 
and  generally  white-washed  on  the  outside  ? 

A.  1st. — Because  straw  is  a  very  bad  con- 
ductor of  heat,  and,  therefore,  prevents  the 
external  heat  from  getting  to  the  ice ;  and 

2nd. — The  white-washed  roof  and  walls 
prevent  the  absorption  of  heat. 

339. 

Q  Why  will  a  little  oil  on  the  surface  of 
water  prevent  its  freezing  ? 

A.  Because  oil  is  a  bad  conductor,  and  pre- 
vents heat  from  leaving  the  water. 


CONDUCTORS  OF  HEAT. 


97 


340. 

Q.  A  silver  tea-si30on  becomes  more 
heated  by  hot  tea,  than  one  of  inferior  me- 
tal, (as  German  silver,  pewter,  etc. ;)  why 
is  this  ? 

A  Because  silver  is  a  better  conductor 
tlian  German  silver  or  pewter. 

Oermnn  silver  is  composed  of  tweuty-five  parts  of  nickel,  twenty-five  cl 
Bine,  and  fifiy  of  copper. 

Pewter  is,  gener.illy  speakincr,  an  alloy  of  tin  and  lead,  sometimes  with 
a  Jitle  antimony  or  copper  combined,  in  different  proportions,  according  to 
the  purposes  for  which  it  is  designed. 

341. 

Q.  Why  does  a  metal  spoon  (left  in  a  sauce- 
pan) retard  the  process  of  boiling  ? 

A.  Because  the  metal  spoon  (being  an 
excellent  conductor)  carries  off  the  heat  from 
the  water  ;  and  (as  heat  is  carried  oflf  by  the 
spoon)  the  water  takes  a  longer  time  to  boil. 

342. 

Q.  Why  does  paint  preserve  wood  ? 

A.  1st. — Because  it  covers  the  surface  of 
the  wood,  and  prevents  both  air  and  damp 
from  penetrating  into  the  pores ; 

2nd. — Because  paint  (especially  white 
paint)  being  a  had  conductor,  preserves  the 
wood  of  a  more  uniform  temperature  ;  and 

3rd.-  — Because  it  fills  up  the  pores  of  the 
wood,  prevents  insects  and  vermin  from 
harboring  therein  and  eating  up  the  fibre. 
9 


98 


CHEMICAL  ACTION. 


343. 

Q.  Why  are  the  fire-irons  intensely  hot^ 
when  they  rest  against  the  stove  which  con- 
tains a  good  fire  ? 

A.  Because  they  are  excellent  conductors  oj 
heaty  and  draw  it  rapidly  from  the  stove  with 
which  they  are  in  contact. 

344. 

Q.  Why  are  tin  foot-warmers  covered  with 
flannel  ? 

A.  1st.— That  the  polish  of  the  tin  may 
not  be  injured ; 

2nd.— Because  the  flannel  (being  a  very 
bad  conductor)  helps  to  keep  the  tin  hot 
longer;  and 

3rd. — Lest  the  conducting  surface  of  the 
tin  should  feel  painfully  hot. 

345. 

Q  What  disadvantage  would  it  be,  if  the 
polish  of  the  tin  were  injured  ? 

A.  If  the  tin  foot- warmer  were  to  lose  its 
polish^  it  would  get  cold  in  a  much  shorter 
time. 

346. 

Q.  Why  are  furnaces  and  stoves  (where 
much  heat  is  required)  built  of  porous  bricks  ? 

A.  Because  bricks  are  bad  conductors,  and 
prevent  the  escape  of  heat ;  in  consequence  of 


CONVECTION. 


99 


which,  they  are  employed  where  great  heat 
is  required. 

347. 

Q.  Why  are  furnace  doors,  etc.,  frequently 
covered  with  a  paste  of  clay  and  sand  ? 

A.  Because  this  paste  is  a  very  bad  con^ 
ductor  of  heat  ;  and,  therefore,  prevents  the 
^cape  of  heat  from  the  furnace, 

343. 

Q.  If  a  stove  be  placed  in  the  middle  of  a 
room,  should  it  be  made  of  bricks  or  iron  ? 

A.  A  stove  in  the  middle  of  a  room  should 
be  made  of  iron  ;  because  iron  is  an  excel- 
lent conductor,  and  rapidly  communicates 
heat  to  the  air  around. 

§  II. — Convection, 
349. 

Q.  What  is  meant  by  the  convection  of 
heat? 

A.  Heat  communicated  by  being  carried 
to  another  thing  or  place ;  as  the  hot  water 
resting  on  the  bottom  of  a  kettle  carries  heat 
to  the  water  through  v/hich  it  ascends. 

350. 

Q,  Are  liquids  good  conductors  of  heat? 
A.  No;  liquids  are  bad  conductors ;  and 
are,  therefore,  made  hot  by  convection. 


100 


CHEMICAL  ACTION. 


351. 

Q.  Why  are  liquids  had  conductors  of  heat  ? 

A.  Because  heat  converts  a  liquid  into 
steam  ;  and  flies  off  with  the  vapor  instear] 
of  being  conducted  through  the  liquid. 

352 

Q.  Explain  how  water  is  made  hot  ? 

A.  The  water  nearest  the  fire  is  first  heat- 
ed, and  (being  heated)  rises  to  the  top  ; 
while  its  place  is  supplied  by  colder  portions, 
which  are  heated  in  turn,  till  all  the  water 
is  boiling  hot 

353. 

Q.  Why  is  water  in  such  continual  fer- 
ment^ when  it  is  boiling  ? 

A.  This  commotion  is  mainly  produced 
by  the  ascending  and  descending  currents  of 
hot  and  cold  water. 

The  eecape  of  steam  from  the  water  contributes  also  to  increase  this  agi- 
tation. 

354. 

Q.  How  do  these  two  currents  pass  eacli 
other  ? 

A.  The  hot  ascending  current  rises  up 
through  the  centre  of  the  mass  of  water ; 
while  the  cold  descending  currents  pass  dowD 
by  the  metal  sides  of  the  kettle. 

Foi  other  questions  on  the  subject  of  l>oil\ng  water,  see  p.  113  etc. 


CONVECTION. 


101 


355. 

Q.  Wliy  is  heat  applied  to  the  bottom y  and 
not  to  the  top  of  a  kettle  ? 

A.  Because  the  heated  water  always 
mcends  to  the  surface,  heating  the  water 
through  which  it  passes ;  if,  therefore,  heat 
were  applied  to  the  top  of  a  vessel,  the  wa- 
fer beloio  the  surface  would  never  be  heated, 

356. 

Q.  As  the  lower  part  of  a  grate  is  made 
red-hot  by  the  fire  Sove,  why  would  not  the 
water  boil,  if  fire  were  applied  to  the  top  of 
a  kettle  ? 

A.  The  iron  of  a  grate  is  an  excellent 
conductor  ;  if,  therefore,  one  part  be  heated, 
the  heat  is  conducted  to  every  other  part ; 
But  water  is  a  very  had  conductor,  and  will 
not  diffuse  heat  in  a  similar  way. 

357. 

Q.  Prove  that  water  is  a  had  conductor  of 
heat  ? 

A.  ^Vhen  a  blacksmith  immerses  his  red- 
hot  iron  in  a  tank  of  water,  the  water  which 
surrounds  the  iron  is  made  hoiling  hot,  while 
that  heloiv  the  surface  remains  quite  cold 

353. 

Q.  If  you  wish  to  cool  liquids,  where 
should  the  cold  be  applied  ? 
9* 


102 


CHEMICAL  ACTION. 


A.  To  the  top  of  the  liquid  ;  because  the 
told  portions  will  always  descend^  and  allow 
the  warmer  parts  to  come  in  contact  with 
tlie  cooUng  substance. 

359. 

Q,  Does  boiling  water  get  hotter  by  be- 
ing kept  on  the  fire  ? 

A  No  ; — not  if  the  steam  be  suffered  to 
escape. 

360. 

Q.  Why  does  not  boiling  water  get  hotter, 
if  the  steam  be  suffered  to  escape  ? 

A.  Because  the  water  is  converted  into 
steam  as  fast  as  it  boils;  and  the  steam 
carries  away  the  additional  heat. 

361. 

Q.  Why  does  soup  keep  hot  longer  than 
boiling  water  ? 

A.  Because  the  grease  and  various  ingre- 
dients floating  in  the  soup,  oppose  the 
ascending  motion  of  the  hot  particles,  and 
prevent  their  rising  so  freely  to  the  surface 

362. 

Q.  If  you  wanted  to  keep  water  hot  for  a 
long  time,  how  could  it  be  done  ? 

A.  By  adding  a  little  starch  or  flour  to 
the  water. 


CONVECTION. 


103 


363. 

Q.  Why  would  a  little  starch,  added  to 
boiling  water,  serve  to  keep  it  hot  ? 

A.  Because  it  would  oppose  the  ascend* 
5iig  motion  of  the  hot  particles  of  water, 
and  j^i'ovent  their  rising  so  freely  to  the 
surface. 

364. 

Q.  Why  do  Indian  mush,  rice  milky  Sfc,  re- 
main hot  longer  than  water  ? 

A.  Because  the  ascending  motion  of  the 
hot  particles  is  opposed  by  the  mush  or 
rice,  and  cannot  so  quickly  reach  the  sur- 
face. 

365 

Q.  How  is  air  heated  ? 

A.  By    convective  currents." 

366. 

Q.  Explain  what  is  meant  by  convective 
currents? 

A.  When  a  portion  of  air  is  heated,  it 
rises  upwards  in  a  current,  carrying  the  heat 
with  it ;  other  colder  air  succeeds,  and  (being 
heated  in  a  similar  way)  ascends  also;  These 
are  called    convective  currents.'^ 


('*  Convective  currents  so  called  from  the  Ljitin  words,  cum-vectui 
\carrieJ  with  ;)  because  the  heat  is  "  carried  with     the  current.) 


104 


CHEMICAL  ACTION. 


367. 

Q.  Is  air  heated  by  the  rays  of  the  sun? 

A.  No ;  air  is  not  heated  (in  any  sensible 
degree)  by  the  action  of  the  sun's  rays  pass- 
ing through  it. 

368. 

Q.  Why  then  is  the  air  hotter  on  a  sunny 
diiy^  than  on  a  cloudy  one  ? 

A.  Because  the  sun  heats  the  surface  of 
the  earth,  and  the  air  (resting  on  the  earth) 
is  heated  hy  contact :  as  soon  as  it  is  heated 
it  ascends ;  while  its  place  is  supplied  by 
colder  portions  which  are  heated  in  turn 
also. 

369. 

Q.  If  air  be  a  had  conductor^  why  does 
hot  iron  become  cold  by  exposure  to  the  air  ? 

A.  Because  it  is  made  cold; 
1st. — By    convection and, 
2nd. — By  ^'radiation." 

370. 

Q.  How  is  hot  iron  made  cold  by  convec- 
tion ? 

A.  The  air  resting  on  the  hot  iron  (being 
intensely  heated,)  rapidly  ascends  with  the 
heat  it  has  absorbed ;  colder  air  succeeding 
ihsiirhs  more  heat  and  ascends  also  ;  and  thii? 


CONVECTION. 


105 


process  is  repeated  till  the  hot  iron  is  cooled 
completely  down. 

371. 

Q.  How  is  broth  cooled  by  being  left  ex< 
posed  to  the  air  ? 

A.  It  throws  off  some  heat  by  radiatim  ; 
but  it  is  mainly  cooled  down  by  convection, 

372. 

Q.  How  is  hot  broth  cooled  down  by  con* 
vection  ? 

A.  The  air  resting  on  the  hot  broth  (being 
heated)  ascends;  colder  air  succeeding  ab- 
sorbs  more  heat,  and  ascends  also;  and  this 
process  is  repeated  till  the  broth  is  made  cool. 

The  particles  on  the  surface  of  the  broth  sink  as  they  are  cooled  down, 
and  warmer  particles  rise  to  the  surface ;  which  gradually  assists  the  cooU 
ing  process. 

373. 

Q.  Why  is  hot  tea  and  broth,  cooled  faster 
by  being  stirred  about  ? 

A.  1st. — Because  the  agitation  assists  in 
bringing  its  hottest  particles  to  the  surface. 

2nd. — The  action  of  stirring  agitates  the. 
air,  and  brings  it  more  quickly  to  the  broth 
or  tea :  and 

3d. — As  the  hotter  particles  are  more 
rapidly  brought  into  contact  with  the  air, 
therefore,  convection  is  more  rapid. 

lilov/ing  tea  or  broth  cools  it  also. 


106 


CHEMICAL  ACTION. 


374. 

Q.  How  does  blowing  hot  food  make  ii 
tool? 

A.  It  causes  the  air  (which  has  been 
lieated  by  the  food)  to  change  more  rapidly, 
and  give  place  to  fresh  cold  air. 

375. 

Q.  If  a  shutter  be  closed  in  the  day- 
time, the  stream  of  light  (piercing  through 
the  crevice)  seems  in  constant  agitation. — 
Why  is  this  ? 

A.  Because  little  7noteB  and  particles  of 
dust  (thrown  into  agitation  by  the  violence 
of  the  convective  currents^)  are  made  visible 
by  the  strong  beam  of  light  thrown  into 
the  room  through  the  crevice  of  the  shut- 
ter. 

376. 

Q.  When  potatoes  are  boiled,  why  are 
those  at  the  top  of  the  boiler,  cooked  sooner 
til  an  those  nearer  the  fire  ? 

A.  1st.— -Because  the  hottest  particles  of 
the  water  rise  to  the  top  of  the  boiler,  and 
the  coldest  particles  sink  to  the  bottom  ;  and 

2nd  — -Because  the  top  of  the  boiler  is 
always  enveloped  with  very  hot  escaping 
Bteam  ;  in  consequence  of  w^hich,  the  pota- 
toes on  the  top  are  subjected  to  more  in- 


CHANGE  OF  STATE 


107 


tense  heat,  than  those  at  the  bottom  of  the 
boiler. 

377. 

Q.  Why  does  milk  boil  more  quickly  than 
water. 

A.  Milk  is  a  thicker  liquid  than  water, 
and  consequently  less  steam  escapes  through 
the  thick  liquid  (milk,)  than  through  the 
thin  liquid  (water;)  therefore,  the  heat  of 
the  whole  mass  of  the  milk  rises  more 
quickly. 

SECTION  III.  CHANGE  OF  STATE. 

378. 

Q.  What  does  change  of  state  mean  ? 

A.  The  change  which  a  substance  under- 
goes on  exposure  to  heat — Thus,  cold  water 
boils,  or  if  the  temperature  be  reduced,  it 
freezes.  Some  solid  substances,  such  as 
wax,  or  metals  change  their  state  and  liquify 
bj  heat. 

379. 

Q  Why  does  melted  wax  become  hard 
^hen  cold? 

A.  Because  the  particles  collapse ;  and, 
being  packed  more  closely  together,  form  a 
solid. 

The  sole  difference  between  a  liquid  and  a  solid,  is  this — In  a  solid  che 
panicles  are  packed  more  closely  together,  than  ihey  are  in  a  liquid.  TTie 
leiidency  of  heat  is  to  drive  the  particles /arf/igr  avart  from  each  othei»  and 
thus  to  liquify  solids. 


108  CHEMICAL  ACTION. 

380. 

Q.  Why  will  hot  iron  bend  more  easily 
than  cold  ? 

A.  Because  it  is  not  so  solid.  The  parti* 
nles  are  driven  farther  apart  by  heat,  and 
the  attraction  of  cohesion  is  thereby  weak- 
c-ned ;  therefore,  the  particles  can  be  made 
10  move  on  each  other  more  readily. 

By  a  still  further  application  of  heat,  the  particles  will  be  driven  so  far 
asunder  from  each  other,  that  the  solid  iron  "will  liquify  ;  in  which  state 
the  particles  will  move  on  each  other  almost  without  resistance. 

381. 

Q.  Why  does  hot  water  freeze  more  quickly 
than  cold  ?  ^ 

A.  Because  there  is  a  slight  agitation  on 
the  surface  of  hot  water,  which  promotes  ^ 
congelation,  by  assisting  the  crystals  to 
change  their  positions,  till  they  take  up  that 
which  is  most  favorable  to  their  solidifica- 
tion. 

Other  caufes  may  have  a  minor  influence,  as  for  example:  In  hot  water, 
♦he  particles  are  subdivided  into  smnller  globules  by  the  heat,  and  offer 
less  resistance  to  the  action  of  cold  than  larger  ones. 

382. 

Q.  Why  are  some  things  solid,  others 
liquid,  and  others  gaseous  ? 

A.  Because  the  particles  which  compose 
some  things  are  nearer  together  than  they 
are  in  others.  Those  in  which  the  parti- 
cles are  closest  are  solid  ;  those  in  which  they 


CHANGE  OF  STATE. 


109 


are  farthest  apart  are  gaseous  ;  and  the  lest 
liquid. 

383. 

Q.  Why  does  heat  change  a  solid  (like 
ice)  first  into  a  liquid,  and  then  into  a  gas 

A  Because  heat  drives  the  component 
jjarticles  farther  asunder;  hence  a  certain 
quantity  of  heat  changes  sohd  ice  into  a 
liquid — and  a  further  addition  of  heat 
changes  the  liquid  into  steam. 

384. 

Q.  Is  steam  visible  or  invisible? 

A.  Steam  is  invisible  ;  but  when  it  comes 
in  contact  with  the  air  (being  condensed  into 
small  drops)  it  instantly  becomes  visible. 

385. 

Q.  How  do  you  know  that  steam  is  irtvi- 
sible  ? 

A.  If  you  look  at  the  spout  of  a  boiling 
kettle,  you  will  find  that  the  steam  (which 
issues  from  the  spout)  is  always  invisible 
for  about  half  an  inch;  after  which  it  be- 
comes visible. 

336. 

Q.  Why  is  the  steam  invisible  for  half  an 
inch  ? 

A.  Because  the  air  is  not  able  to  con* 
10 


110 


CHEMICAL  ACTION. 


dense  it,  as  it  first  issues  from  the  spout ; 
but  when  it  spreads  and  comes  in  contact 
with  a  larger  volume  of  air,  the  invisible 
steam  is  readily  condensed  into  visible  drops. 

3S7. 

Q.  Why  do  steam  engines  sometimes  burst  1 
A.  Because  steam  is  very  elastic;  and 
this  elasticity  increases  in  a  greater  propor- 
tion than  the  heat  which  produces  it ;  un- 
less, therefore,  some  vent  be  freely  allowed, 
steam  will  burst  the  vessel  which  confines 
it. 

§  I. — Latent  Heat. 
388. 

Q.  Why  does  steam  burn  so  much  more 
severely  than  boiling  water  ? 

A.  Steam  condenses  as  soon  as  it  is  ex- 
posed to  the  cold,  and  gives  out  all  the  heat 
by  w^hich  it  was  produced  ;  therefore,  as  one 
thousand  degrees  of  heat  become  latent  in 
steam,  it  gives  out  that  amount  when  con- 
densed, which  is  much  greater  than  boiling 
water. 

389. 

Q.  Is  there  heat  even  in  ice  ? 
A.  Yes ;  but  it  is  latent  (that  is,  not  per* 
ceptible  to  our  senses.) 

Latent,  fiom  the  Latin  word,  Laleo,  ^to  lie  hid.) 


LATENT  HEAT. 


Ill 


390. 

Q.  How  do  you  know  there  is  heat,  if 
you  cannot  perceive  it  ? 

A.  Thus  :  The  temperature  of  ice  is  32'' 
by  the  thermometer ;  but  if  ice  be  melted 
over  0  fire,  (though  140''  of  heat  are  ab- 
sorbed by  the  process)  it  will  feel  no  hotter 
than  before. 

391. 

Q.  What  becomes  of  the  140°  of  heat 
which  w^ent  into  the  ice  to  melt  it  ? 

A.  It  is  hidden  in  the  water;  or  (to  speak 
more  scientifically)  it  is  stored  up  in  a  laterit 
state, 

392. 

Q.  How  much  heat  may  be  thus  secreted 
or  made  latent  ? 

A.  All  things  contain  a  vast  quantity  of 
latent  heat;  but  as  much  as  1140°  of  heat 
may  remain  latent  in  water. 

393. 

Q.  How  can  1140°  of  heat  be  added  ti) 
water  without  being  perceptible  to  our  feel- 
ings ? 

A.  1st. — 140°  of  heat  are  hidden  in  wa- 
ter, when  ice  is  melted  by  the  sun  or  fire  ; 

2nd. — 1000°  more  of  heat  are  secreted, 
when  water  is  converted  into  steam.  Thus, 


112 


CHEMICAL  ACTION. 


before  ice  is  converted  into  steam,  1140°  of 
heat  become  latent. 

One  pint  of  boiling:  water  (212°  according  to  the  thernjometer)  wil 
make  eighteen  hundred  pints  of  steam;  but  the  steam  is  no  hotter  to  the 
touch  than  boiling  water ;  both  are  212*^,  therefore,  when  water  is  coo' 
verted  into  s-team,  1000^  of  heal  become  latent.    Hence,  before  ice  i& 
Verted  into  steam,  it  must  contain  1140'^  of  latent  heat. 

394. 

Q.  Why  does  cold  water  poured  on  lime 
make  it  intensely  hot  ? 

A.  Because  heat  is  evolved  by  the  chemi- 
cal action  which  takes  place,  when  the  cold 
water  combines  with  the  lime. 

N.  B.  Heat  is  always  evoZfed,  when  a  fluid  is  converted  into  a  solid  form. 
Heal  is  always  absorbed^  when  a  solid  is  changed  into  a  liquid  state.  Aa 
the  water  is  changed  from  its  liquid  form  when  it  is  taken  up  by  the  lime 
therefore,  heat  is  given  off. 

335. 

Q.  Where  does  the  heat  come  from  ? 
A.  It  was  in  the  water  and  lime  before  ; 
but  was  in  a  latent  state. 

396. 

Q.  Was  there  heat  in  the  cold  water  and 
lime  before  they  were  mixed  together  ? 

A.  Yes ;  All  bodies  contain  heat ;  the 
coldest  ice  as  well  as  the  hottest  fire. 

397. 

Q.  Explain  by  illustration  what  you 
mean  ? 

A.  Water  is  cold,  and  sulphuric  «icid  ia 
cold  ;  but  if  these  two  cold  liquids  be  mixed 
together,  they  will  produce  intense  heat. 


EBULLITION. 


113 


§  II. — Ebulliiion, 
393. 

Q.  What  is  ebullition  ? 

A.  Ebullition,  or  boiling,  is  occasioned  by 
the  formation  of  bubbles  o£  vapor  within  the 
body  of  the  evaporating  liquid,  which  rise 
t^:  the  surface  and  then  break. 

399. 

Q.  Do  all  liquids  boil  at  the  same  temper- 
ature ? 

A.  No  ;  the  boiling  point  occurs  in  differ- 
ent liquids  at  very  different  temperatures. 

400. 

Q.  Why  does  milk  boil  over  more  readily 
than  water  ? 

A.  Because  the  bubbles  of  milk^  produced 
by  the  process  of  boiling,  are  more  tenacious 
than  the  bubbles  of  water ;  and  these  bub- 
Wes,  accumulating  and  climbing  one  above 
another,  soon  overtop  the  rim  of  the  sauce- 
pan and  run  over. 

401. 

Q.  Why  does  water  simmer  before  it  boils? 

A.  Because  the  particles  of  water  7iear 
the  bottom  of  the  kettle  (being  formed  into 
steam  sooner  than  the  rest)  shoot  upwards ; 
but  are  condensed  again  (as  they  rise)  by  t\e 
colder  water,  and  produce  what  is  cnlled 
simmering." 

10* 


114 


CHEMICxa  ACTION. 


402. 

Q.  What  is  meant  by  simmering  ? 

A.  A  gentle  tremor  or  undulation  on  the 
surface  of  the  water.  When  water  simmers^ 
the  bubbles  collapse  beneath  the  surface,  and 
the  steam  is  condensed  to  water  again  ;  but 
Avhen  water  boils,  the  bubbles  rise  to  the  sur* 
face,  and  the  steam  is  thrown  off. 

Collapse,  that  is,  burst. 

403. 

Q.  Why  does  a  kettle  sing  when  the  watei 
simmers  ? 

A.  Because  the  air  (entangled  in  the  wa- 
ter) escapes  by  Jits  and  starts  through  the 
spout  of  the  kettle,  which  makes  a  noise  like 
a  wind  instrument. 

404. 

Q.  Why  does  not  a  kettle  sing  when  the 
water  boils  ? 

A.  Because  all  the  water  is  boiling  hot ; 
so  the  steam  escapes  in  a  continuous  stream, 
and  not  by  fits  and  starts. 

405. 

Q.  When  does  a  kettle  sing  most? 
A.  ^Vlien  it  is  set  on  the  dde  of  the  firt 
to  boil 

406. 

Q  Why  does  a  kettle  sing  more  when  W 


EBULLITION. 


115 


is  set  oil  the  side  of  a  fire,  than  Avlien  it  is 
set  in  the  midst  of  the  fire  ^ 

A.  Because  the  heat  is  appHed  so  mu 
equally,  that  one  side  is  made  hotter  than  the 
other  ;  in  consequence  of  which,  the  steam 
is  more  entangled. 

407. 

Q.  Why  does  a  kettle  sing,  when  the  boil- 
ing water  begins  to  cool  again  ? 

A.  Because  the  upper  surface  cools  jirst ; 
and  the  steam  (which  rises  from  the  lower 
part  of  the  kettle)  is  again  entangled^  and 
escapes  by  fits  and  starts. 

403. 

Q.  ^Yhy  does  boiling  water  swell  ? 

A.  Because  it  is  expanded  by  the  heat ; 
that  is — The  heat  of  the  fire  drives  the  par- 
ticles of  water  farther  apart  from  each  other ; 
and  (as  they  are  not  packed  so  closely  together) 
they  take  up  more  room  ;  in  other  words,  the 
water  swells. 

409. 

Q  What  is  meant  when  it  is  said,  that 
'^heat  drives  the  particles  of  water  farther 
apart  from  each  other?" 

A.  Water  is  composed  of  little  globules, 
like  very  small  grains  of  sand ;  the  heat 
drives  these  particles  away  from  each  other ; 


116 


CHEMICAL  ACTION. 


and  (as  they  then  require  more  rooin)  the 
water  swells. 

410. 

Q.  Why  does  boiling  ivaier  bubble  ? 

A .  Because  the  vapor  (rismg  through  the 
water)  is  entangled,  and  forces  up  bubbles  in 
its  effort  to  escape. 

N.  B.  All  liie  air  of  water  is  expelled  at  the  commencemeni  of  its  boiling 
411. 

Q.  ^¥lly  does  a  kettle  sometimes  boil  over  ? 

A.  Because  the  water  is  expanded  by  heat ; 
if,  therefore,  a  kettle  is  filled  with  cold  water , 
some  of  it  must  run  over,  as  soon  as  it  is  ex- 
panded  by  heat. 

412. 

Q.  But  I  have  seen  a  kettle  boil  over, 
although  it  has  not  been  filled  full  of  water ; 
how  do  you  account  for  that  ? 

A,  If  a  fire  be  very  fierce,  the  air  and  va- 
por are  expelled  so  rapidly,  that  the  bubbles 
are  very  numerous  ;  and  (towering  one  above 
another)  reach  the  top  of  the  kettle,  and  fall 
over. 

413. 

Q.  Why  is  a  pot  (w^hich  was  full  to  over- 
flowing, while  the  water  was  boiling  hot)  not 
full,  after  it  has  been  taken  off  the  fire  for 
1  sliort  time  ? 


EBULLITION 


A.  Because  (while  the  water  is  boiling)  it 
is  expanded  by  the  heat,  and  fills  the  pot 
even  to  overflowing ;  but,  when  it  becomes 
cool,  it  contracts  again,  and  occupies  a  inncl> 
less  space. 

414. 

Q.  Why  does  the  water  of  a  kettle  run  jui 
of  the  spout  when  it  boils  ? 

A.  Because  the  lid  fits  so  tightly,  that 
the  steam  cannot  lift  it  up  and  escape ,  be- 
ing confined,  therefore,  in  the  kettle,  it 
presses  on  the  water  with  great  power,  and 
forces  it  out  of  the  spout. 

415. 

Q.  What  causes  the  rattling  noise^  so  often 
made  by  the  lid  of  a  saucepan  or  boiler  ? 

A.  The  steam  (seeking  to  escape)  forces 
up  the  lid  of  the  boiler,  and  the  loeight  of 
the  lid  carries  it  back  again;  this  being  done 
frequently,  produces  a  rattling  noise. 

416. 

Q.  If  the  steam  could  not  lift  up  the  lid  of 
the  boiler,  how  would  it  escape  ? 

A.  If  the  lid  fitted  so  tightly,  that  tlie 
steam  could  not  raise  it  up,  the  boiler  would 
hurst  into  fragments,  and  the  consequences? 
might  be  fatal. 

417. 

Q.  When  steam  pours  out  from  the  spout 


118 


CHEfflCAL  ACTION. 


of  a  kettle,  the  stream  begins  apparently  halj 
an  inch  off  the  spout ;  why  does  it  not  be- 
gin close  to  the  spout  ? 

A.  Steam  is  really  invisible  ;  and  the  half 
inch  (between  the  spout  and  the  ''stream  of 
mist'')  is  the  real  steam,  before  it  has  been 
condensed  by  air. 

418. 

Q.  Why  is  not  all  the  steam  invisible  as 
v/ell  as  that  half-inch  ? 

A.  Because  the  invisible  particles  are 
condensed  by  the  cold  air ;  and,  rolling  one 
into  another,  look  like  a  thick  mist. 

419 

Q.  What  becomes  of  the  steam  ?  for  it  soon 
vanishes. 

A.  After  it  has  been  condensed  into  mist, 
it  is  dissolved  by  the  air,  and  dispersed  abroad 
as  invisible  vapor. 

420. 

Q.  And  what  becomes  of  the  invisible  vapoi  ? 

A.  Being  lighter  than  air,  it  ascends  to  tlje 
upper  regions  of  the  atmosphere,  where 
(being  again  condensed)  it  contributes  to  form 
douds. 

421. 

Q.  Why  will  a  pot  (filled  with  water) 
never  boil,  when  immersed  in  another  vessel 
full  of  water  also  ? 


EBULLITION. 


119 


A.  Because  water  can  never  be  heated 
above  the  boiling  point ;  all  the  heat  absorbed 
by  water  after  it  boils y  is  employed  in  gene- 
rating steam-, 

422. 

Q.  How  does  the  conversion  of  water 
into  steam,  prevent  the  inner  pot  from  hoiU 
ing  ? 

A.  As  soon  as  the  water  in  the  larger 
pot  is  boiling  hot  (or  212"*,)  steam  is  formed 
and  carries  off  some  of  its  heat ;  therefore, 
212"*  of  heat  can  never  pass  through  it,  to 
raise  the  inner  vessel  to  boiling  heat, 

423. 

Q.  Why  do  sugar,  salt,  ^c,  retard  the  pro- 
cess of  boiling  ? 

A.  Because  they  increase  the  density  of 
water ;  and  whatever  increases  the  density 
of  a  fluid,  retards  its  boiling. 

424. 

Q.  If  you  want  water  to  boil  without 
the  vessel  containing  it  coming  in  contact 
with  the  fire,  what  plan  must  you  adopt  ? 

A.  We  must  immerse  the  vessel  (containinjL; 
tlie  water  to  be  boiled^  in  a  saucepan  con- 
taining boiling  brine,  or  syrup. 

475. 

Q.  AVliy  would  the  inner  vessel  boil,  if 
the  outer  vessel  contained  boiling  brine  ^ 


120 


CHEMICAL  ACTION- 


A.  Because  brine  will  not  boil,  till  it  ia 
raised  to  218"  or  220^  Therefore,  212"  of 
heat  may  easily  pass  through  it,  to  raise  th. 
vessel  immersed  in  it  to  boiling  heat, 

426. 

Q.  Wh}^  will  brine  impart  to  another  ves- 
sel more  than  212°,  and  water  not  so  much  ? 

A.  Because  no  liquid  can  impart  so  high 
a  degree  of  heat,  as  its  own  boiling  tempe- 
rature :  As  water  boils  at  212"  it  cannot 
impart  212"  of  heat :  but,  as  brine  will  not 
boil  without  218"  of  heat,  it  can  impart 
enough  to  make  water  boil. 

427. 

Q.  Why  can  liquids  impart  no  extra  heat, 
after  they  boil  ? 

A.  Because  all  extra  heat  is  spent  in 
making  steam.  Hence  water  will  not  boil  a 
vessel  of  water  immersed  in  it,  because  it 
cannot  impart  to  it  212"  of  heat ;  but  brine 
will,  because  it  can  impart  more  than  212" 
of  heat,  before  it  is  itself  converted  into 
steam. 


Ether  boils  at    .    .  100  degs. 

Alcohol,       .    .    .  173^  " 

Wnter,     .    .    .    ,  212 
Water,  with  one- 

fiflhsah,    .    .  219  " 


Syrup  boils  at    .    .  21  deg$  • 

Oil  of  Turpentine, .  314  " 

Sulphuric  acid,  .    .  472  " 

Linseed  oil,  .    .    .  640  " 

Mercury,  ....  656 


Ar.y  liquid  which  boils  at  a  lower  degree  can  be  made  to  boil,  if  in 
merged  in  a  liquid  which  boils  at  a  higher  degree.  Thus  a  cup  of  ether  van 
be  made  to  boil  in  a  saucepan  of  water.  A  cup  of  water  in  a  saucepan  of 
hrine  or  syrvp.  But  a  rvp  of  water  will  not  boil,  if  immersed  in  ether  ;  nor 
a  rvp  of  syrvp  in  water. 


EVAPORATION. 


121 


§  111 — Evavoration, 
428. 

Q   What  is  meant  by  evaporation  ? 
A.  The  dissipation  of  liquid  by  its  i^on- 
version  into  vapor. 

429. 

Q.  What  effects  are  produced  by  evapora- 
tion? 

A.  The  liquid  vaporized  absorbs  heat  from 
the  body  whence  it  issues ;  and  the  body 
deprived  of  the  liquid  by  evaporation,  loses 
heat. 

430. 

Q.  If  you  wet  your  finger  in  your  mouth, 
and  hold  it  up  in  the  air,  why  does  it  feel 
cold? 

A.  Because  the  saliva  quickly  evaporates ; 
and  (as  it  evaporates)  absorbs  heat  fro7n  the 
finger,  making  it  feel  cold. 

431. 

Q.  If  you  bathe  your  temples  with  ether, 
why  does  it  allay  inflammation  and  feverish 
heat  ? 

A.  Because  ether  very  rapidly  evaporates; 
and  (as  it  evaporates)  absorbs  heat  from  the 
hnrning  head,  producing  a  sensation  of  cold. 

432. 

Q  Why  is  ether  better  for  this  purpose 
than  xoater? 

11 


122  CHEMICAL  ACTION. 

A.  Because  ether  requires  less  heat  to  con 
vert  it  into  vapor  ;  in  consequence  of  which, 
it  evaporates  more  quickly. 

N.  B.  Ether  is  converted  into  vapor  with  100°  of  heat;  but  water  rt^ 
quires  21?^  of  heat  to  convert  it  into  steam, 

433. 

Q.  Why  does  ether  very  greatly  relieve  a 
scald  or  hum  ? 

A.  Because  it  evaporates  very  rapidly:  and 
(as  it  evaporates)  carries  off  the  heat  of  the 
burn. 

434. 

Q.  Why  do  we  feel  cold^  when  we  have 
wet  feet  or  clothes? 

A.  Because  the  wet  of  our  shoes  or 
clothes  rapidly  evaporates;  and  (as  it  evapo- 
rates) absorbs  heat  from  our  body,  which 
makes  us  feel  cold. 

435. 

Q.  Why  do  wet  feet  or  clothes  give  us 
cold?'' 

A.  Because  the  evaporation  absorbs  heat 
hO  abundantly  from  the  surface  of  our  body, 
that  its  temperature  is  lowered  belou)  its  natur 
ral  standard;  in  consequence  of  which, 
health  is  injured. 

436. 

Q.  Why  is  it  dangerous  to  sleep  in  a  damp 
bed? 


EVArORATIOiN. 


128 


A.  Because  the  heat  is  contmually  ab- 
sorbed from  the  surface  of  our  body,  to  ton- 
virt  the  damp  of  the  sheets  into  vapor ;  hi 
consequence  of  which,  our  animal  heat  is 
reduced  helow  the  healthy  standard. 

437. 

Q.  Why  is  health  injured^  when  the  tem- 
perature of  the  body  is  reduced  below  its  na- 
tural standard  ? 

A.  Because  the  balance  of  the  circulation 
is  destroyed.  Blood  is  driven  away  from 
the  external  surface  by  the  chilly  and  thrown 
upon  the  internal  organs,  which  are  oppressed 
by  this  increased  load  of  blood. 

438. 

Q.  Why  do  we  not  feel  the  same  sensa- 
tion of  cold,  if  we  throw  a  macinto'ih*  over 
our  wet  clothes  ? 

A.  Because  the  macintosh  (being  air 
tight)  prevents  evaporation:  and  (as  the  wet 
cannot  evaporate)  no  heat  is  absorbed  from 
our  bodies. 

439. 

Q.  Why  do  not  sailors  get  cold,  who  are 
frequently  wet  all  day  with  sea-water  ? 

A.  1st. — Because  the  salt  of  the  sea  re- 
tards evaporation  ;  and  (as  the  heat  of  their 

*A  macintosh  is  a  waterproof-coal. 


124 


CIIEMCAL  ACTION. 


body  is  drawn  off  gradually)  the  sensation 
of  cold  is  i)revented. 

2nd. — The  salt  of  the  sea  acts  as  a  stimu- 
lant, and  keeps  the  blood  circulatmg  in  the 
skin. 

440. 

Q.  Why  does  sprinkling  a  hot  room  with 
water  cool  it  ? 

A.  Because  the  heat  of  the  room  causes 
a  rapid  evaporation  of  the  sprinkled  water: 
and  as  the  water  evaporates,  it  absorbs  heat 
from  the  room,  which  cools  it. 

441. 

Q.  Why  is  it  customary,  in  very  hot  conn- 
tries,  to  sit  in  rooms  separated  by  curtains, 
instead  of  walls  or  doors;  and  to  keep  these 
curtains  constantly  sprinkled  with  water  ? 

A.  Because  curtains  are  bad  conductors 
of  heat ;  and  the  rapid  evaporation  of  water 
reduces  the  temperature  of  the  room  ten  or 
fifteen  degrees. 

442. 

Q.  Why  does  watering  the  streets  and 
roads  cool  them  ? 

A.  Because  they  part  with  their  heat  to 
promote  the  evaporation  of  the  water  sprinkled 
rm  them. 


EVAPORATION. 


125 


443. 

Q.  Why  does  a  shower  of  I'aiit  toul  the 
flfr  ii)  summer-time  ? 

A.  Because  the  wet  earth  parts  with  its 
hmt  to  promote  evaporation :  and  when  the 
earth  is  cooled,  it  cools  the  air  also. 

444. 

Q.  Why  is  linen  dried  by  being  exposed 
to  the  wind  ? 

A.  Because  the  wind  accelerates  evapora- 
tion,  by  removing  the  vapor  from  the  sur- 
face  of  the  ivet  linen ^  as  fast  as  it  is  formed. 

445. 

Q.  Why  is  linen  dried  sooner  in  the  open 
air^  than  in  a  confined  room  ? 

A.  Because  the  particles  of  vapor  are 
more  rapidly  removed  from  the  surface  of 
the  linen  by  evaporation. 

446. 

Q.  Why  are  wet  summers  generally  suc- 
ceeded by  cold  winters  ? 

A.  Because  the  great  evaporation  (car- 
ried on  through  the  wet  summer)  reduces 
the  temperature  of  the  earth  lower  than  usual ^ 
and  produces  cold. 

447. 

Q.  Why  are  our  eastern  and  many  of  oui 
western  states  warmer,  and  the  winters  less 
j^rere  than  formerly? 

11* 


]26  CHE^UaVL  ACTION. 

A.  Because  they  are  better  drained  and 
better  rMltivated. 

448. 

Q.  Why  does  draining  land  promote 
warmth  ? 

A,  Because  it  diminishes  evaporation ;  in 
consequence  of  which,  less  heat  is  abstracted 
from  the  earth. 

449. 

Q.  Why  does  cultivation  increase  the 
warmth  of  a  country  ? 

A.  1st. — Because  hedges  and  belts  of  trees 
are  multiplied : 

2nd. — The  land  is  better  drained :  and 

3rd. — The  vast  forests  are  cut  down. 

450. 

Q.  Why  do  hedges  and  belts  of  trees  pro- 
mote warmth  ? 

A.  Because  they  retard  evaporation y  b> 
keeping  off  the  wind. 

451. 

Q.  If  belts  of  trees  promote  loarmthy  why 
do  forests  produce  cold? 

A.  1st. — Because  they  detain  and  con- 
dense thp  passing  clouds : 

2nd. — They  prevent  the  access  of  both 
v:ind  and  sun : 


EVAPORATION. 


127 


3rd. — The  soil  of  forests  i:^  always  covered 
w^th  long  damp  grass,  rotting  leaves^  and  thick 
brushwood:  and 

4th. — In  every  forest  there  are  always 
many  hollows /z///  of  stagnant  water. 

452. 

Q.  Why  do  long  grass  and  rotting  leaves 
jiromote  cold  ? 

A.  Because  they  are  always  damp ;  and 
evaporation,  which  they  promote,  is  con- 
stantly  absorbing  heat  from  the  earth  be- 
neath. 

453. 

Q.  Why  are  France  and  Germany  warmer 
now,  than  when  the  vine  would  not  rij)en 
there  ? 

A.  Chiefly  because  their  vast  forests  have 
been  cut  down;  and  the  soil  is  better  drained 
and  cultivated. 

454. 

Q.  What  becomes  of  the  water  of  ponds  in 
summer-time  ? 

A.  Ponds  are  often  left  dry  in  summer- 
time, because  their  water  is  evaporated  by  the 
air. 

455. 

Q.  How  is  this  evaporation  produced  and 
carried  on  ? 


128 


CHEMICAL  ACTION. 


A.  The  heat  of  the  air  changes  the  siu 
face  of  tM  ivater  into  vapor ^  which  (blending 
with  the  air)  is  soon  wafted  away  ;  and  simi- 
lar  evaporation  is  repeatedly  produced,  till 
the  pond  is  left  quite  dry. 

456. 

Q.  Why  are  the  wheels  of  some  machines 
kept  constantly  wet  with  water  ? 

A.  To  carry  off  (by  evaporation)  the  heat 
which  arises  from  the  rapid  motion  of  the 
wheels. 

457. 

Q.  Why  is  the  surface  of  the  ground 
hardened  by  the  sun  ? 

A.  Because  the  moisture  of  the  ground  is 
exhaled  by  evaporation  ;  and,  as  the  earthy 
particles  are  brought  closer  together,  the 
mass  becomes  more  solid. 

458. 

Q.  Show  the  wisdom  of  God  in  this  ar- 
rangement. 

A.  If  the  soil  did  not  become  crusty  and 
hard  in  dry  weather,  the  heat  and  drought 
would  penetrate  the  soil,  and  kill  both  seeds 
and  roots. 

459. 

Q.  Why  does  bread  become  hard  al'tor  it 
has  been  kept  a  few  days  ? 


EVAPORATIO^. 


129 


A.  Because  the  vapor  and  gases  escape, 
leaving  the  solid  particles  dry  ;  so  that  they 
collapse  and  become  more  solid  and  hard» 

460. 

Q.  Why  are  glue^  g^^,  starch  and  paste 
adhesive  ? 

A.  Because  the  water  used  wiih  them  ra- 
pidly evaporates,  and  leaves  them  solid  ;  and 
they  insinuate  themselves  so  intimately 
into  the  pores  of  the  substances  with  which 
they  come  in  contact,  that  when  the  water 
evaporates,  the  whole  is  one  solid  mass. 

They  lose  their  adhesiveness  when  dissolved  in  water;  and,  tlierefire, 
must  always  be  suffered  to  become  dry,  before  they  will  hold  with  tenacity 

461. 

Q.  YvTiy  is  tea  cooled  faster  in  a  saucer 
than  in  a  cup  ? 

A.  Because  evaporation  is  increased  by  in- 
creasing the  surface  ;  and,  as  tea  in  a  saucer 
presents  a  larger  surface  to  the  air,  its  heat  is 
more  rapidly  carried  off  by  evaporation. 

It  is  also  cooled  by  convection — (See  Chap.  III.,  Sec.  II.,  §  II.) 
462. 

Q.  Why  is  not  the  vapor  of  the  sea  salt  ? 
A.  Because  the  salt  is  always  left  behind, 
in  the  process  of  evaporation. 

463. 

Q.  What  is  that  white  crust,  which  ap- 


130 


CHEMICAL  ACTION. 


pears  (in  hot  weather)  upon  ckthes  wetted 
by  sea  water  ? 

A.  The  salt  of  the  water,  left  on  the 
clothes  by  evaporation. 

464. 

Q,  Why  does  this  white  crust  always  dis- 
appear in  wet  weather  ? 

A.  Because  the  moisture  of  the  air  dissolves 
the  salt ;  in  consequence  of  which,  it  is  no 
longer  visible. 

465. 

Q.  Why  should  not  persons,  who  take 
violent  exercise,  wear  very  thick  clothing  ? 

A.  Because  it  prevents  the  perspiration 
from  evaporating.  When  the  heat  of  the 
body  is  increased  by  exercise,  perspiration 
reduces  the  heat  (by  evaporation)  to  a  healthy 
standard;  as  thick  clothing  prevents  this 
evaporation,  it  is  injurious  to  health. 

466. 

Q.  Wliy  will  not  lucifer  matches  ignite 
if  they  are  damp  ? 

A.  1st. — Because  the  cold,  produced  hy 
the  evaporation  of  the  water,  neutralizes  the 
heat  produced  by  the  friction  of  the  match 
across  the  bottom  of  the  lucifer  box ;  and, 

2nd. — Because  the  damp  prevents  the 
free  accession  of  oxygen  to  the  match,  with- 
r>ut  which  it  cannot  burn. 


VAPORIZATION. 


133 


467. 

Q,  Why  does  water  in  a  very  exposed 
place  freeze  more  rapidly,  than  that  which 
is  under  cover,  or  in  a  place  less  exposed  ? 

A.  1st. — Because  evaporation  goes  on 
more  rapidly  when  water  is  exposed ;  and 
carries  away  heat  from  the  general  mass ; 
and, 

2nd. — Any  covering  will  radiate  hmt  into 
the  water  below,  and  prevent  the  mass  from 
cooling  down  to  the  requisite  temperature 
to  cause  congelation. 

468. 

Q.  Why  does  paint  often  blister  from  heat? 

A.  Because  the  heat,  penetrating  through 
paint,  extracts  some  little  moisture  from  the 
wood,  and  turns  it  into  vapor  or  steam.  As 
this  vapor  requires  room,  it  throws  up 
blisters  in  the  paint  to  make  room  for  it?! 
expanded  bulk. 

§  IV. — Vaporization, 
469. 

Q.  What  is  meant  by  vaporization  ? 

A.  The  conversion  of  a  solid  or  liquid  into 
vapor  ;  as  snow  or  water  is  converted  into 
vapor  by  the  heat  of  the  sun. 


132 


CHEMICAL  ACTION. 


470. 

Q.  Explain  the  difference  between  eva- 
poration and  vaporization  ? 

A.  Evaporation  is  effected  by  exposure 
to  the  air,  without  boiling ;  whilst  vapori- 
zation requires  the  air  of  sufficient  heat  to 
produce  ebullition. 

"  Ebullition,**  boiling. 
471. 

Q.  Why  does  hot  iron  make  a  hissing 
noise  when  plunged  into  water  ? 

A.  Because  the  hot  iron  converts  into 
steam,  the  particles  of  water  which  come  in 
immediate  contact  with  it;  and,  as  the 
steam  flies  upwards,  it  passes  by  other  par- 
ticles of  water  not  yet  vaporized  ;  the  colli- 
sion produces  very  rapid  vibrations  in  the 
air,  and  a  hissing  noise  is  the  result. 

472. 

Q.  Why  does  ivater  make  a  hissing  noise 
v/hen  it  is  j)oured  on  fire  ? 

A.  Because  the  part  which  comes  in  con- 
tact with  the  fire  is  immediately  converted 
into  steam  ;  and,  as  it  flies  upward,  meets 
other  particles  of  water  not  yet  vaporized  ; 
the  collision  produces  very  rapid  vibra- 
tions in  the  air,  and  a  hissing  noise  is  the 
result. 


VAPORIZATION, 


133 


473. 

Q.  Why  is  water  converted  into  steam  hy 
the  heat  of  the  fire  ? 

A.  Because,  when  the  heat  of  the  fire  en- 
ters the  water,  it  separates  its  globules  into  very 
rTzmw/epar/fc/e^;  which  (being  lighter  than  air) 
Oy  off  from  the  surface  in  the  form  of  steam. 

474. 

Q.  Why  do  doors  swell  in  rainy  weather? 

A.  Because  the  air  is  filled  with  vapor, 
which  (penetrating  into  the  pores  of  the 
wood)  forces  its  particles  farther  apart ,  and 
swells  the  door. 

475. 

Q.  Why  do  doors  shrink  in  dry  weather  ? 

A.  Because  the  moisture  is  absorbed  from 
the  wood ;  and,  as  ihe  particles  are  brought 
closer  together,  the  size  of  the  door  is  lessened 
— in  other  words,  the  wood  shrinks. 

476. 

Q.  Why  is  the  air  filled  with  offensive 
smells,  just  previous  to  a  coming  rain  ? 

A.  Because  the  volatile  parts  which  rise 
from  dunghills,  sewers,  etc.,  are  prevented 
(by  the  vapor  of  theazV)  from  mmg  so  readily, 
as  when  the  sun  is  shining  brightly. 

477. 

Q.  Why  do  flowers  smell  sweeter  and 
stronger,  just  previous  t)  rain? 
12 


134 


CHEMICAL  ACTION. 


A.  Because  the  volatile  particles  wliici 
constitute  the  perfume  of  flowers,  are  pre- 
vented (by  the  vapor  of  the  air)  from  risino: ; 
in  consequence  of  which,  they  are  confined 
to  the  lower  regions  of  the  atmosphere. 

N  B.  MaTiy  essential  oils  and  other  volatile  substances,  which  produce 
odors  in  plants,  require  the  presence  of  much  moisture  for  their  perfect 
developement. 

478. 

Q.  Why  do  horses  and  other  animals 
stretch  out  their  necks,  and  snuff  up  the  air^ 
just  pre  vious  to  a  fall  of  rain  ? 

A.  Because  they  smell  the  odor  of  plants 
and  hay,  and  delight  to  snuiBF  in  their  fra- 
grance. 

479. 

Q.  Why  does  smoke  fall,  when  rain  is  at 
hand  ? 

A.  Because  the  air  is  less  dense,  and  can- 
not buoy  up  the  smoke  so  readily  as  dry  and 
heavy  air. 

480. 

Q.  Wh}^  does  a  downward  current  of  cold 
air  bring  rain  ? 

A .  Because  it  condenses  the  warm  vapor ; 
which  (being  condensed)  descends  in  rain. 

481. 

Q.  Why  does  a  drop  of  water  sometimes 
roll  along  a  piece  of  hot  iron,  without  leav- 
uig  the  least  trace  ? 


LIQUEFACTION . 


135 


A.  Because  the  bottom  of  the  drop  is 
turned  into  vapor,  which  buoys  the  drop  up, 
without  allowing  it  to  touch  the  iron. 

482. 

Q.  Why  does  it  roll  ? 

A.  Because  the  current  of  air  (which  is 
always  passing  over  a  heated  surface)  drives 
'/  alcng. 

483 

Q.  Why  does  a  laum^  ess  put  a  little  saliva 
on  a  flat-iron,  to  know  if  it  be  hot  enough  ? 

A.  Because  when  the  saliva  sticks  to  the 
iron,  and  is  evaporated,  she  knows  it  is  not 
sufficiently  hot ;  but,  when  it  runs  along  the 
iron,  it  is. 

484. 

Q.  Why  is  the  flat-iron  hotter  if  the  saliva 
runs  along  it,  than  if  it  adheres  till  it  is 
evaporated  ? 

A.  Because  when  the  saliva  runs  along 
the  iron,  the  heat  is  sufficient  to  convert  the 
bottom  of  the  drop  into  vapor ;  but,  if  the 
saliva  will  not  roll,  the  iron  is  not  sufficiently 
hot  to  convert  the  bottom  of  the  drop  into 
vapor- 

§  \r, — Liquefaction 
485. 

Q.  What  is  meant  by  liquefaction? 


136 


CHEAOCAL  ACTION. 


A.  The  state  of  being  melted ;  as  ice  is 
melted  by  the  heat  of  the  sun. 

486. 

Q  Why  is  ice  melted  by  the  heat  of  (he 
sun  ? 

A.  Because,  when  the  heat  of  the  mn 
enters  the  solid  ice,  it  forces  its  particles 
asunder  ;  till  their  attraction  of  cohesion  is 
sufficiently  overcome,  to  convert  the  solid  ice 
into  a  liquid. 

487. 

Q.  The  temperature  of  ice  is  32° ;  if  you 
pour  just  enough  boiling  water  over  the  ice 
to  melt  it,  will  the  temperature  of  the  wa- 
ter be  increased  ? 

A.  No ;  the  heat  of  the  water  is  con- 
sumed in  melting  the  ice  ;  but  pour  boilhig 
water  on  ice-cold  water,  and  the  tempera- 
ture is  immediately  increased. 

483. 

Q.  Why  does  wax  become  soft  before  it 
turns  liquid  ? 

A.  Because  it  absorbs  heat  sufficient  to 
loosen  the  contact  of  its  particles,  before  it 
has  absorbed  sufficient  to  liquefy  the  mass. 

489. 

Q.  Why  are  metals  melted  by  the  heat  of 
fire? 


RADIATION. 


137 


A.  Because,  when  the  heat  of  the  lire 
enters  the  solid  metal,  it  forces  its  particles 
asvnder  ;  till  their  attraction  of  cohesion  is 
vsufficiently  overcome,  to  convert  the  solid 
metal  into  a  liquid. 

490. 

Q.  Why  does  not  wood  melt  like  metal  ? 

A.  Because  the  heat  of  the  fire  decom- 
poses the  wood  into  gas,  smoke,  and  ashes ; 
and  the  different  parts  separate  from  each 
other. 

491. 

Q.  Why  does  salt  crackle  when  thrown 
into  the  fire  ? 

A.  Salt  contains  water  ;  and  the  crackling 
of  the  salt  is  owing  to  the  sudden  conversion 
of  this  water  into  steam. 

SECTION  IV.  RADIATION 

492. 

Q.  What  is  meant  by  radiation  ? 

A.  Radiation  means  the  emission  of  rays  ; 
thus  the  sun  radiates  both  light  and  heat ; 
that  is,  it  emits  rays  of  light  and  heat  in  all 
directions. 

493. 

Q.  When  is  heat  radiated  from  one  body 
to  another? 

12^ 


138 


CHEMICAL  ACTION. 


A.  When  the  two  bodies  are  separated  by 
a  non-conducting  medhim ;  thus  the  sun  ra- 
diates heat  towards  the  earth,  because  the  air 
(whicli  is  a  very  bad  conductor)  comes  he^ 
I  ween. 

494. 

Q.  On  what  does  radiation  depend? 

A.  On  the  roughness  of  the  radiating  sur- 
face; thus,  if  metal  he  scratched y  its  radiating 
power  is  increased ;  because  the  heat  has 
more  points  to  escape  from. 

495. 

Q.  Does  a  fire  radiate  heat  ? 

A.  Yes;  and  because  burning  fuel  emits 
rays  of  heat,  therefore,  we  feel  warm  when 
we  stand  before  a  fire. 

496. 

Q.  Why  does  our  face  feel  uncomfortably 
hot  when  we  approach  a  fire  ? 

A.  Because  the  fire  radiates  heat  upon 
the  face ;  which  (not  being  covered)  feels 
the  effect  immediately. 

497. 

Q.  Why  does  the  fire  heat  the  face  more 
than  it  does  the  rest  of  the  body  ? 

A.  Because  the  rest  of  the  body  is  covered 
with  clothing;  which  (being  a  had  cnri. 


RADIATION. 


139 


ductor  of  heat)  prevents  the  same  sudden 
and  rapid  transmission  of  heat  to  the  skin. 

498. 

Q.  Do  those  substances  which  ^-adiate  heat 
absorb  heat  also  ? 

A.  Yes.  Those  substances  which  )  adiaff' 
most,  also  absorb  most  heat ;  and  those  which 
radiate  least,  also  absorb  the  least  heat. 

499. 

Q.  Does  anything  dse  radiate  heat  besides 
the  sun  and  fire  ? 

A.  Yes ;  all  things  radiate  heat  in  some 
measure,  but  not  equally  well, 

500. 

Q.  What  things  radiate  heat  the  next  best 
to  the  sun  and  fire  ? 

A.  All  dull  and  dark  substances  are  good 
radiators  of  heat ;  but  all  light  and  polished 
substances  are  bad  radiators. 

501. 

Q.  What  is  meant  by  being  a  "bad  radia- 
tor  of  heat?'' 

A.  To  radiate  heat  is  to  throw  o  f  heat  by 
rays,  as  the  sun ;  a  polished  tin  pan  does 
not  throio  off  the  heat  of  boiling  water  from  its 
Burface,  but  keeps  it  in. 


CHEMICAL  ACTION 


£02. 

Q.  Why  is  a  tin  pan  (filled  with  hot  water  j 
as  a  foot-warmer  ? 

A.  Because  polished  tin  (being  a  bad  ra- 
diator of  heat)  keeps  hot  averylon^  time; 
and  warms  the  feet  resting  upon  it. 

503. 

Q.  Why  would  the  tin  foot-warmer  get 
cold  sooner^  if  the  polish  were  injured  ? 

A.  Because  polished  tin  throws  off  its  heat 
very  slowly  ;  but  dull,  scratched,  painted,  or 
dirty  tin,  throws  off  its  heat  very  quickly. 

504. 

Q.  Why  does  snow  (at  the  foot  of  a  hedge 
or  loall)  melt  sooner  than  that  in  an  open 
field? 

A.  Because  the  hedge  or  wall  radiates 
heat  into  the  snow  beneath,  which  melts  it. 

505 

Q,  How  is  hot  iron  cooled  by  radiation  ? 

A.  While  its  heat  is  being  carried  off  by 
"convection,''  the  hot  iron  throws  off  heat 
(on  all  sides)  hy  radiation  also. 

506. 

Q.  Why  should  the  flues  (connected  with 
stoves,  etc.,)  be  always  blackened  ^Yith  black 
lead^ 

A  ,  In  order  that  the  heat  of  the  fine  moy 


RADIATION 


141 


be  more  readily  difused  throughout  the 
room .  Black  lead  radiates  heat  more  freely 
than  any  other  known  substance. 

In  lieaiinnf  a  room  with  steam  it  would  be  absurd  to  use  black  pipti  (as 
coiiveyijiff  the  feieam,  because  ihey  would  tend  to  cool  the  ho  vapor, 

507. 

Q.  Why  does  a  polished  metal  tea-pot  make 
better  tea  than  a  black  earthen  one  ? 

A.  Because  polished  m?tal  (being  a  very 
bad  radiator  of  heat)  keeps  the  water  hot  much 
longer;  and  the  hotter  the  water  is,  the 
better  it    draws"  the  tea. 

508. 

Q.  Why  will  not  a  dull  black  tea-pot  make 
good  tea  ? 

A.  Because  the  heat  of  the  water  flies  of 
so  quickly  through  the  dull  black  surlace  of 
the  tea-pot,  that  the  water  is  very  rapidly 
cooled,  and  cannot  "draw"  the  tea. 

509. 

Q.  Do  not  the  poorer  classes  generally 
prefer  the  little  black  earthen  tea-pot  to  the 
bright  metal  one  ? 

A.  Yes ;  because  they  set  it  near  the  fire 
^^to  draw  ;"  in  which  case,  the  little  black 
tea-poi  will  make  the  best  tea. 

510. 

Q.  Why  will  a  black  tea-pot  make  better 


142 


CHEMICAL  ACTION. 


tea  than  a  bright  metal  one,  if  it  be  set  neai 
the  fire  to  draw  ? 

A.  Because  the  black  tea-pot  will  ahsorb 
heat  plentifully  from  the  fire,  and  keep  the 
water  hot ;  whereas  a  bright  metal  tea-pot 
(set  near  the  fire)  would  throw  off  the  heat 
by  reflection. 

511. 

Q.  Then  sometimes  a  black  earthen  tea- 
pot is  the  best,  and  sometimes  a  bright 
metal  one  ? 

A.  Yes ;  when  a  tea-pot  is  set  on  the 
stove  "to  draw^^  black  earth  is  the  hest^  be- 
cause it  absorbs  heat ;  but,  when  a  tea-pot  is 
not  set  on  the  stove,  bright  metal  is  the  best ; 
because  it  radiates  heat  very  slowly^  and, 
therefore,  keeps  the  water  hot. 

512. 

Q.  Would  a  metal  pot  serve  to  keep  wa- 
ter hot  if  it  were  dull  and  dirty  ? 

A.  No.  It  is  the  bright  polish  of  the 
metal  which  makes  it  a  bad  radiator  ;  if  it 
were  duU^  scratched^  or  dirty y  the  heat  would 
escape  very  rapidly. 

Wate^  in  hot  weather  is  also  kept  cooler  in  bright  raeta  than  in  dull  oi 
earthen  vessels. 

513. 

Q,  Why  are  dinner-covers  made  of  hrighl 
tin  or  nlver  ? 


RADIATION. 


143 


A  Because  light-colored  and  highly- 
polished  metal  is  a  very  had  radiator  of  heat ; 
and,  therefore,  bright  tin  or  silver  will  not 
allow  the  heat  of  the  cooked  food  to  escape 
through  the  cover  by  radiation. 

514. 

Q.  Why  should  a  meat-cover  be  very 
brightly  polished  ? 

A.  To  prevent  the  heat  of  the  food  from 
escaping  from  radiation.  If  a  meat-cover 
be  dull  or  scratched,  it  will  absorb  heat  from 
the  food  beneath  ;  and,  (instead  of  keeping  it 
hot)  make  it  cold, 

515. 

Q.  Wliy  should  a  silver  meat -cover  be  plain 
and  not  chased  ? 

A.  Because  a  chased  meat-cover  woukl 
absorb  heat  from  the  food  ;  and  (instead  of 
keeping  it  hot)  make  it  cold. 

516. 

Q.  Why  is  meat  very  subje<3t  to  taint  on 
a  moonlight  night  ? 

A.  'Because  it  radiates  heat  very  freely  in 
a  bright  moonlight  night ;  in  consequence 
of  which,  it  is  soon  covered  with  deio% 
which  produces  rapid  decomposition, 

517 

Q.  How  do  moonlight  nights  conduce  to  the 
rapid  grovjth  of  plants. 


144 


CHEl\nCAL  ACTION. 


A.  Radiation  is  carried  on  very  rapidly 
on  bright  moonlight  nights;  in  consequence 
of  which,  dew  is  very  plentifully  deposited 
on  young  jolants,  which  conduces  much  to 
their  growth  and  vigor. 

518. 

Q.  Why  is  the  air  (resting  on  the  surface 
of  the  earths  colder  than  that  in  the  higher 
regions  ? 

A.  Because  the  earth  radiates  more  heat 
than  the  leaves  of  lofty  trees ;  and,  there- 
fore, more  rapidly  condenses  and  freezes  the 
vapor  of  the  air. 

519. 

Q.  Why  are  shrubs  more  liable  to  be 
frost-bitten  than  trees. 

A.  Because  they  do  not  rise  far  above 
the  surface  of  the  earth ;  and  (as  the  air 
contiguous  to  the  earth  is  made  colder  by  ra- 
diation than  that  in  the  higher  regions,) 
therefore,  the  low  shrub  is  often  frost-bitten^ 
when  the  lofty  tree  is  uninjured. 

SECTION  V.  REFLECTION. 

520. 

Q.  What  is  meant  by  reflecting  heat  ? 
A.  To  reflect  heat  is  to  throw  it  hack  in 


REFLECTION. 


145 


rays  from  the  surface  of  the  reflecting  body 
towards  the  place  whence  it  came. 

521 

Q.  What  are  the  best  reflectors  of  heat  ? 
A,  All  bright  surfaces  and  light  colors. 

522. 

Q  Are  good  absorbers  of  heat  good  refleC' 
tors  also  ? 

A.  No;  those  things  which  absorb  heat 
best,  reflect  heat  worst ;  and  those  which  re- 
flect heat  loorst,  absorb  it  best. 

523. 

Q.  Why  are  those  things  which  absorb 
heat  unable  to  reflect  it? 

A.  Because  if  anything  sucks  in  heat  like 
a  sponge,  it  cannot  throw  it  off  from  its  sur- 
face ;  and  if  anything  throws  off  heat  from 
its  surface,  it  cannot  drink  it  in. 

524. 

Q.  Why  are  reflectors  always  made  of 
light  colored  and  highly  polished  metal  ? 

A.  Because  light  colored  and  highly  po- 
lished metal  makes  the  best  of  all  reflectors. 

525. 

Q.  Why  do  not  plate-warmers  blister  and 
fjcorch  the  wood  behind  ? 

A.  Because  the  bright  tin  front  throws 
(he  heat  of  the  fire  back  again,  and  will  not 
ullow  it  to  penetrate  to  the  wood  behind. 
13 


U6 


CHEMICAL  ACTION. 


526. 

Q.  If  metal  be  such  an  excellent  conduc- 
tor of  heat,  how  can  it  reflect  heat,  or  ihrow 
it  off? 

A.  Polished  metal  is  a  conductor  of  heat 
only  when  that  heat  is  communicated  by 
actual  contact :  but  whenever  heat  falls  upon 
bright  metal  in  rays,  it  is  reflected  back  again, 
and  the  metal  remains  cool. 

527. 

Q.  What  is  meant  "  by  heat  falling  upon 
metal  in  rays,^^  and  not  "  by  contact 

A.  If  a  piece  of  metal  were  thrust  into 
a  fire,  it  would  be  in  actual  contact  with  the 
fire  ;  but  if  it  were  held  before  a  fire,  the 
heat  of  the  fire  would  fall  upon  it  in  rays, 

528. 

Q.  Why  is  a  plate-warmer  made  of  un- 
painted  bright  tin  ? 

A.  Because  bright  tin  reflects  the  heat 
(which  issues  from  the  fire  in  rays)  upon 
the  meat ;  and,  therefore,  greatly  assists  the 
process  of  roasting. 

Reflects  the  heat,  that  is,  throws  it  lack  upon  the  meat. 

529. 

Q.  What  is  the  use  of  the  tin  screen  or 
reflector  used  in  roasting  ? 

A.  It  throws  the  heat  of  the  fire  back  upon 
fhe  meat  ;  and,  therefore,  both  assists  the 


REFLECTION. 


147 


process  of  roasting,  and  helps  to  keep  th^ 
kitchzn  cool. 

530. 

Q.  How  does  a  tin  reflector  tend  to  keep 
(he  kitchen  cool? 

A.  By  confining  the  heat  of  the  fire  to 
the  hearth,  and  preventing  its  disj)ersion 
throughout  the  kitchen. 

531. 

Q.  Why  would  not  the  tin  reflector  do  as 
well,  if  it  were  painted  ? 

A.  Because  it  would  then  absorb  heat,  and 
not  reflect  it  at  all.  A  plate-warmer  should 
never  be  painted,  but  should  be  kept  very 
clean,  bright,  and  free  from  all  scratches. 

532. 

Q.  Wliy  should  a  reflector  be  kept  so  very 
clean  and  free  from  all  scratches  ? 

A.  Because  if  a  reflector  were  spotted, 
didl,  or  scratched,  it  would  absorb  heat,  in- 
stead of  reflecting  it;  and,  consequently, 
would  be  of  no  use  whatsoever  as  a  re- 
flector. 

533. 

Q.  Why  will  not  a  polished  tin  pan,  bake 
bread  as  well  as  an  iron  one  ? 

A.  Because  the  bright  metal  reflects  the 
heat ;  and,  therefore,  will  not  brown  the 


lis 


CHEMICAL  ACTION. 


enist  which  surrounds  the  bottom  and  side^i 
of  the  pan ;  consequently,  the  top  of  the 
bread  would  be  burnt  before  the  bottom  and 
sides  of  the  loaf  were  brown. 

534. 

Q.  ^Yliy  will  a  kettle  be  slower  boiling  if 
the  bottom  and  sides  are  clean  and  bright  ? 

A.  Because  bright  metal  does  not  absorb 
heat,  but  reflects  it;  and  (as  the  heat  is 
thrown  off  from  the  surface  of  bright  metal 
by  reflection)  therefore,  a  new  kettle  takes 
a  longer  time  to  boil. 

Reflects  heat,  that  Is,  throws  it  off. 
535. 

Q.  Why  do  persons  xoear  lohite  dresses  in 
summer  time  ? 

A.  Because  white  throws  off  the  heat  of 
the  sun  by  reflection,  and  is  a  very  bad  ab- 
sorbent of  heat ;  in  consequence  of  w^iich, 
white  dresses  never  become  so  hot  from  the 
scorching  sun  as  dark  colors  do. 

536. 

Q.  Why  do  not  persons  wear  white  dressea 
in  winter  time  ? 

A.  Because  white  will  not  absorb  heat,  like 
black  and  other  dark  colors  j  and,  there- 
fore, white  dresses  are  not  so  ivarm  as  dark 
ones. 


ABSORPTION. 


149 


537. 

Q.  Why  are  shoes  hotter  for  being  dusty  ? 

A.  Because  dull,  dusty  shoes  will  absorb 
heat  from  the  sun,  earth,  and  air ;  but  shoes 
brightly  polished  throw  off  the  heat  of  the 
mn  by  reflection. 

SECTION  VI.  ABSORPTION. 

538. 

Q.  What  is  the  difference  between  con- 
ducting heat,  and  absorbing  heat  ? 

A.  To  conduct  heat  is  to  transmit  it  from 
one  body  to  another  through  a  conducting 
medium.  To  absorb  heat  is  to  suck  it  up^  as 
a  sponge  sucks  U23  water. 

539. 

Q.  Give  me  an  example  ? 

A.  Black  cloth  absorbs,  but  does  not  con- 
duct heat ;  thus,  if  black  cloth  be  laid  in  the 
sun,  it  will  absorb  the  rays  very  rapidly  ;  but 
if  one  end  of  the  black  cloth  be  made  hot,  it 
would  not  conduct  the  heat  to  the  other  end. 

540 

Q.  Are  good  conductors  of  heat  good  ab- 
sorbers also  ? 

A.  No  ;  Every  good  conductor  of  heat  is  a 
had  absorber  of  it ;  and  no  good  absorber  of 
hc-at  can  Ije  ^  good  conductor  also. 
13* 


150 


CHEMICAL  ACTION. 


541. 

Q.  Is  iron  a  good  absorber  of  heat  ? 
A.  No;  iron  is  a  good  conductor^  but  a 
very  bad  absorber  of  heat. 

542. 

Q.  Why  do  the  fire-irons  (which  lie  upon 
Cl fender)  remain  cold,  although  they  are  be- 
fore a  good  fire  ? 

A.  Because  they  are  bad  absorbers  of  heat; 
in  consequence  of  which,  they  remain  cold, 
unless  they  come  in  contact  with  the  stove 
or  fire. 

543. 

Q.  If  a  piece  of  brown  paper  be  submitted 
to  the  action  of  a  burning  glass,  it  will  catch 
fire  much  sooner  than  a  piece  of  white  paper 
would ;  explain  the  reason  ? 

A.  Because  white  paper  reflects  the  rays 
of  the  sun,  or  throws  them  back  ;  in  conse- 
quence of  which,  it  appears  more  luminous, 
but  is  not  so  much  heated  as  dark  brorun 
paper,  which  absorbs  the  rays,  and  readily 
becomes  heated  to  ignition. 

Besides,  brown  paper  is  of  a  looker  and  more  combustible  fabric  than 
while  paper. 

544. 

Q.  Why  is  the  temperature  of  islands  moro 
equable  than  that  of  continents  ? 

A.  Because  the  loater  around  the  island 


ABSORPTION. 


151 


absorbs  the  extreme  heat  of  summer;  and 
gives  out  heat  to  mitigate  the  extreme  cold 
of  winter. 

545. 

Q.  Islands  are  warmer  in  winter  than  con- 
tinents.   Explain  the  reason  of  this  ? 

A.  Unless  the  sea  be  frozen  (which  is 
rarely  the  case)  it  is  warmer  than  the  frozen 
land ;  and  the  warmth  of  the  sea-air  helps 
to  mitigate  the  intense  cold  of  the  land-air. 

546. 

Q.  How  does  the  ceaseless  change  of  air 
tend  to  decrease  the  loarmth  of  a  nalved 
body? 

A.  Thus: — the  air  (which  cases  the 
body)  absorbs  as  much  heat  from  it  as  it 
can,  while  it  remains  in  contact;  being  then 
blown  away,  it  makes  room  for  a  fresh  coat 
of  airy  which  absorbs  more  heat. 

547. 

Q.  Does  the  air  which  encases  a  naked 
body,  become  (by  contact)  as  warm  as  the 
hodj  itself? 

A.  It  would  do  so,  if  it  remained  motion- 
less ;  but,  as  it  remains  only  a  very  short 
time,  it  absorbs  as  much  heat  as  it  can  in 
the  time,  and  passes  on. 


152 


CHEMICAL  ACTION. 


548. 

Q.  Why  does  fanning  the  face  in  summei 
make  it  cool  ? 

A.  Because  the  fan  puts  the  air  in  motion, 
and  makes  it  pass  more  rapidly  over  the  face;. 
and  (as  the  temperature  of  the  air  is  always 
lower  than  that  of  the  human  face)  each  puff 
of  air  carries  off  some  portion  of  its  heat. 

549. 

Q.  Why  do  ladies  fan  themselves  in  hot 
weather? 

A.  That  fresh  particles  of  air  may  be 
brought  in  contact  with  their  faces  by  the 
action  of  the  fan  ;  and  as  every  fresh  parti- 
cle of  air  absorbs  some  heat  from  the  skin, 
this  constant  change  makes  them  cool. 

550. 

Q.  Does  a  fan  cool  the  air  ? 

A.  No;  it  makes  the  air  hotter  by  im- 
parting to  it  the  heat  out  of  onr  face  ;  but 
it  cools  our  face  by  transferring  its  heat  to 
(he  air. 

551. 

Q.  Does  /(Qfnnmg  make  the  a/r  itself  coo/^r? 
A.  No  ;  fanning  makes  the  air  hotter  and 
hotter. 

552. 

Q.  How  does  fanning  the  face  increase 
tlie  heat  of  the  air  ? 


ABSORPTION. 


A.  By  driving  the  air  more  rapidly  over 
the  liuman  body,  and  causing  it,  consequent- 
ly, to  absorb  more  heat. 

553. 

Q.  If  fanning  makes  the  air  hotter ^  why 
can  it  make  a  person  feel  cooler  ? 

A.  Because  it  takes  the  heat  out  oj  Iht 
face,  and  gives  it  to  the  air. 

554. 

Q.  Why  is  hroth  cooled  by  blowing  it  ? 

A.  Because  the  breath  causes  a  rapid 
change  of  air  to  pass  over  the  broth ;  and 
(as  the  air  is  colder  than  the  broth)  it  con- 
tinually absorbs  heat  from  it,  and  makes  it 
cooler  and  cooler. 

555. 

Q.  Would  not  the  air  absorb  heat  from 
the  broth  just  as  well  without  bloiving  ? 

A.  No;  air  is  a  very  bad  conductor ;  unless, 
therefore,  the  change  be  rapid ,  the  air  nearest 
the  surface  of  the  broth  would  soon  become  a.s 
hot  as  the  broth  itself, 

556. 

Q  Would  not  hot  air  part  with  its  heat 
instantly  to  the  circumjacent  air  ? 

A.  No ;  not  instantly.  Air  is  so  bad  a 
conductor,  that  it  parts  wdth  its  heat  very 
doiuhj  ;  unless,  therefore,  the  air  be  kept  in 


154 


CHEMICAL  ACTION. 


continual  ?notiony  it  would  cool  the  broth  ver^ 
slowly  indeed. 

557. 

Q.  Why  does  wind  generally  feel  cool? 

A.  Because  it  drives  the  air  more  rapidly 
over  our  body ;  and  this  rapid  change  of  air 
draws  off  a  large  quantity  of  heat. 

558. 

Q.  Why  does  air  absorb  heat  more  quickly 
by  being  set  in  motion  ? 

A.  Because  every  fresh  gust  of  air  absorbs 
1  fresh  portion  of  heat ;  and  the  more  rapid 
the  succession  of  gusts,  the  greater  will  be 
the  quantity  of  heat  absorbed. 

559 

Q.  If  the  air  were  hotter  than  our  body, 
would  the  wind  feel  cool  ? 

A.  No ;  the  air  would  feel  insufferably 
hot,  if  it  were  hotter  than  our  body 

560. 

Q.  Why  would  the  air  feel  intensely  hot, 
\  f  it  were  warmer  than  our  body  ? 

A.  Because  it  would  add  to  the  heat  of 
our  body,  instead  of  diminishing  it. 

561 

Q.  Is  the  air  ever  as  hot  as  the  human 
hody? 


ABSORPTION. 


155 


A.  In  some  climates  it  is,  and  when  that 
is  the  case  the  heat  is  almost  insupportable , 

Q.  Why  does  a  kettle  boil  faster,  when 
the  bottom  and  sides  are  covered  with  soot  1 

A.  Because  the  hladz  soot  absorbs  heat  very 
quickly  from  the  fire,  and  the  metal  conducts 
it  to  the  water. 

563. 

Q.  Why  will  not  a  new  kettle  boil  so  fast  as 
an  old  one  ? 

A.  Because  the  bottom  and  sides  of  a  new 
kettle  are  clean  and  bright ;  but  in  an  old 
kettle  they  are  covered  with  soot,  or  black- 
ened by  the  fire. 

564. 

Q.  Why  do  we  wear  white  linen  and  a 
black  outer  dress,  if  we  want  to  be  warm  ? 

A.  Because  the  black  outer  dress  quickly 
absorbs  heat  from  the  sun ;  and,  the  white 
linen  (being  a  bad  absorbent)  abstracts  no 
heat  from  the  warm  body 

533. 

Q.  What  colors  are  warmest  for  dresses  ? 

A.  For  outside  garments  black  is  the 
warmest,  and  then  such  colors  as  approach 
nearest  to  black,  (as  dark  blue  and  green.) 
White  is  the  coldest  color  for  external  clothing. 


56 


CHEMICAL  ACTION. 


566. 

Q.  Why  are  dark  colors  (for  external 
wear)  so  much  warmer  than  light  ones  ? 

A.  Because  dark  colors  absorb  heat  from 
the  sun  more  abundantly  than  light  ones. 

567. 

Q.  How  can  you  prove  that  dark  color? 
tire  warmer  than  light  ones  ? 

A.  If  a  piece  of  black  and  a  piece  of 
lohite  cloth  were  laid  uj)on  snow,  in  a  few 
hours  the  black  cloth  will  have  melted  the  snow 
beneath  ;  whereas,  the  ivhite  cloth  will  have 
produced  little  or  no  effect  upon  it  at  all, 

N.  B.  The  darker  any  color  is,  the  warmer  it  is,  because  it  is  a  better 
absorbent  of  heat.  The  order  may  be  thus  arranged  : — 1,  Black  (warmesi 
of  all  )— 2,  Violet.--3,  Indigo.— 4,  Blue.— 5,  Green.— 6,  Red.— 7  Yellow  : 
and  8,  while  (coidest  of  all.) 

568. 

Q.  Why  are  black  kid  gloves  unpleasantly 
hot  for  summer  wear  ? 

A.  1st. — Because  black  absorbs  the  solar 
heat ;  and 

2nd. — Kid  will  not  allow  the  heat  of  our 
hand  to  escape  readily  through  the  glove. 

569. 

Q.  Why  are  Lisle  f  read  gloves  agreeably 
cool  for  summer  wear  ? 

A.  1st. — Because  thread  absorbs  perspiru' 
Hon:  and 


ABSORPTION 


157 


2nd. — It  conducts  away  the  heat  of  our 
hot  hands. 

570. 

Q.  Are  Lisle  thread  gloves  absorbents  of 
heat  ? 

A.  No;  Lisle  thread  gloves  are  generally 
of  a  grey  or  lilac  color ;  and,  therefore,  do 
vot  absorb  solar  heat. 

571 

Q.  Why  does  hoar  frost  remain  on  to7nb' 
stones  long  after  it  has  melted  from  the 
grass  and  gravd-walks  of  a  church-yard  ? 

A.  Because  tomb-stones  (being  white) 
will  not  absorb  heat,  like  the  darker  grass 
and  gravel ;  in  consequence  of  which,  they 
remain  too  cold  to  thaw  the  frost  congealed 
upon  their  surface. 

572. 

Q.  If  black  absorbs  heat,  why  have  ne'> 
groes  black  skins,  and  not  white  skins,  which 
would  not  absorb  heat  at  all  ? 

A.  Because  black  will  not  blister  from  the 
heat  of  the  sun.  Although,  therefore,  the 
black  skin  of  the  negro  absorbs  heat  more 
plentifully  than  the  white  skin  of  a  Euro- 
pean ;  yet  the  blackness  prevents  the  sun 
from  blistering  or  scorching  it, 

573. 

Q  How  is  it  known  that  the  black  color 
14 


i58 


CHElVnCAL  ACTION. 


prevents  the  sun  from  either  blistering  os 
scorching  the  skin  ? 

A*  If  you  put  a  white  glove  on  one  hand, 
and  a  black  glove  on  the  other  (when  the  sun 
is  burning  hot,)  the  hand  with  the  white 
love  will  be  scorched,  but  not  the  other. 

574. 

Q   Which  hand  will  feel  the  hotter  ? 

A.  The  hand  with  the  black  glove  will 
feel  the  hotter,  but  will  not  be  scorched  by 
the  sun  ;  whereas,  the  hand  with  the  tvhite 
glove  (though  much  cooler)  will  be  severely 
scorched. 

575. 

Q.  Why  does  the  black  skin  of  a  negro 
never  scorch  or  blister  with  the  hot  sun  ? 

A.  Because  the  black  color  absorbs  the  heat 
— conveys  it  below  the  surface  of  the  skin — 
and  converts  it  to  sensible  heat  and  perspira- 
tion. 

576. 

Q.  Why  does  the  white  European  skin 
blister  and  scorch  when  exposed  to  the  hot 
sun  ? 

A.  Because  white  will  not  absorb  hen^t;  and, 
therefore,  the  hot  sun  rests  on  the  surface  of 
the  skin,  and  scorches  it. 

577. 

Q.  Wliy  has  a  negro  black  eyes  ? 


ABSORPTION. 


150 


A.  Because  the  black  color  defends  them 
from  the  strong  light  of  the  tropical  sun. 
If  a  negro's  eyes  were  not  black,  the  sun 
would  scorch  them. 

578. 

Q.  Why  is  water  (in  hot  weather)  kept 
cooler  in  a  bright  tin  pot  than  in  an  earthen 
one  ? 

A.  Because  bright  metal  will  not  absorb 
heat  from  the  hot  air,  like  an  earthen  vessel; 
in  consequence  of  which,  the  water  is  kept 
cooler. 

Boiling  water  is  also  kept  hot  in  bright  metal  better  than  m  earthen 
vessels. 

579. 

Q.  Why  does  a  saucepan,  which  has  been 
used,  boil  in  a  shorter  time  than  a  new  one  ? 

A.  Because  the  bottom  and  sides  are 
covered  with  soot ;  and  black  soot  rapidly  ab- 
sorbs the  heat  of  the  glowing  coals. 

580. 

Q.  Why  should  the  lid  of  a  saucepan  be 
clean  and  bright  ? 

A.  Because  it  cannot  absorb  heat,  as  it 
does  not  come  in  contact  with  the  fire ;  and 
(being  bright)  it  will  not  suiFer  the  heat  to 
escape  by  radiation. 

581. 

Q.  In  what  state  should  a  saucepan  be,  in 
order  that  it  may  boil  quickly  ? 


160 


CHEMICAL  ACTION. 


A.  All  those  parts  which  come  in  contact 
with  the  firCy  should  be  covered  with  soot,  or 
be  black,  in  order  to  absorb  heat ;  but  all 
the  rest  of  the  saucepan  should  be  as  bright 
as  possible,  to  prevent  the  escape  of  heat  hy 
radiation. 

582. 

Q.  Why  should  not  the  bottom  and  sides 
of  a  kettle  be  cleaned  and  polished  ? 

A.  Because  they  come  in  contact  with  the 
fire,  and  (while  they  are  covered  with  black 
soot)  absorb  heat  freely  from  the  burning 
coals. 

583. 

Q.  Why  should  the  top  of  a  kettle  be 
clet  n  and  well  polished  ? 

A.  Because  polished  metal  ivill  not  ra- 
diate heat ;  and,  therefore,  (while  the  top  of 
the  kettle  is  well  polished)  the  heat  is  kept  in, 
and  not  suffered  to  escape  by  radiation. 

584. 

Q.  Show  the  benefit  of  smoke  in  cooking  ? 

A.  The  carbon  of  the  fuel  (which  flies 
off  in  smoke)  naturally  blackens  all  culinary 
vessels  set  upon  the  fire  to  boil,  and  thus 
renders  them  fit  for  use. 

**  Culinary  vessels  "  are  vessels  used  in  kitchens  for  cooking,  as  sauo/} 
wans,  boilers,  kettles,  etc..  (from  the  Laliw  word  "  Cullna,"  akiteken,) 


PERCUSSION. 


161 


585. 

Q  How  does  smoke  make  culinary  vessels 
(it  for  use  ? 

A.  By  absorbing  heat.  If  it  were  not 
ft>r  the  smoke  (which  gathers  round  a  kettle 
01  saucepan)  heat  would  not  he  absorbed,  and 
the  process  of  boiling  would  be  greatly  re- 
tarded. 

586. 

Q.  Why  is  boiling  water  kept  hot  in  a 
bright  metal  pot  better  than  in  an  earthen 
vessel  ? 

A.  Because  bright  metal  (being  a  had  ra- 
diator) will  not  throw  off  from  its  surface  the 
heat  of  the  boiling  water. 


CHAP.  IV.— MECHANICAL  ACTION. 

SECTION  I.  PERCUSSION. 

587. 

Q.  How  is  heat  j)roduced  by  mechanica) 
action? 

A.  1. — By  Percussion.  2. — By  Friction, 

and  3. — 1^Y  Condensation,  or  Compression . 

588. 

Q.  ^Yhat  is  meant  by  percussion  ? 

A.  The  act  of  striking  ;  as  when  a  black- 
smith  strikes  a  piece  of  iron  on  his  anvil 
Mrith  his  hammer. 

11* 


162 


MECHANICAL  ACTION* 


589. 

Q.  Why  does  striking  iron  make  it  red  hot'! 
A.  Because  it  condenses  the  particles  of  the 
meta]^  and  makes  the  latent  heat  sensible. 

530. 

Q.  Does  cold  iron  contain  heat  ? 
A.  Yes ;  everything  contains  heat ;  but, 
when  a  thing  feels  cold,  its  heat  is  latent. 

591. 

Q.  What  is  meant  by  latent  heat  ? 

A.  Heat  not  perceptible  to  our  feelings. 
When  anything  contains  heat  without  feel- 
ing  the  hotter  for  it,  that  heat  is  called  ''la- 
tent heat'' 

592. 

Q.  Does  cold  iron  contain  latent  heat? 

A.  Yes ;  and  when  a  blacksmith  com- 
presses the  particles  of  iron  by  his  hammer, 
he  brings  out  latent  heat ;  and  this  makes 
the  iron  red  hot. 

593. 

Q.  How  used  blacksmiths  to  light  their 
matches  before  the  general  use  of  lucifers  ? 

A.  They  used  to  lolace  a  soft  iron  nail 
upon  their  anvil ;  strike  it  tw^o  or  three 
times  with  a  hammer ;  and  the  point  be* 
came  snfficieiithj  hot  to  light  a  brimstone  m.a,fch 


PERCUSSION. 


163 


594. 

Q.  How  can  a  nail  (beaten  by  a  hammer) 
ignite  a  brimstone  match  ? 

A.  The  particles  of  the  nail  being  com- 
py^ssed  by  the  hammer,  can  no  longer  con- 
tain so  mnch  heat  in  a  latent  state^  as  th^.y 
did  before ;  some  of  it,  therefore,  becomes 
sensible,  and  increases  the  temperature  of 
the  iron. 

595. 

Q.  Why  does  striking  a  flint  against  a 
piece  of  steel  produce  a  spark  ? 

A.  Because  it  compresses  those  parts  of 
the  flint  and  steel  which  strike  together.  In 
consequence  of  which,  some  of  their  latent 
heat  is  disturbed,  and  exhibits  itself  in  a 
spark. 

596. 

Q.  How  does  this  development  of  heat 
produce  a  spark  and  set  tinder  on  fire  ? 

A.  A  very  small  fragment  (either  of  the 
steel  or  flint)  is  knocked  off  red  hot,  and  gets 
fire  to  the  tinder  on  which  it  falls. 

597. 

Q.  Why  is  it  needful  to  keej)  blowing  Iho 
tinder  with  the  breath  ? 

A.  In  order  that  the  increased  supply  oi* 
air  may  furnish  the  tinder  with  more  oxygen 
to  assist  combustion. 


164 


MECHANICAL  ACTIOI^ 


598. 

Q.  Where  does  the  oxygen  of  the  air  comi 
from  J  wliich  is  blown  to  the  lighted  tinder  r 

A.  From  the  air  itself,  which  is  composed 
of  two  gases  {nitrogen  and  oxygen)  mixed  to- 
gether. 

Every  five  gallons  of  common  air  contain  nearly  four  gallons  of  nitro- 
gon,  and  one  of  oxygen. 

599. 

Q.  What  is  the  use  of  oxygen  gas  to  light- 
ed tinder  ? 

A.  It  supports  the  combustion  of  the  tinder. 
Blowing  lighted  tinder  carries  oxygen  to  it 
and  quickens  it,  in  the  same  way  as  a  pair 
of  bellows  quickens  a  dull  fire. 

600. 

Q.  Why  do  horses  sometimes  strike  fire 
with  WiQiY  feet? 

A.  Because  when  their  iron  shoes  strike 
against  the  flint  stones  of  the  road,  very 
small  fragments  (either  of  the  shoe  or  stones) 
are  knocked  o  f  red  hot,  and  look  like  sparks. 

601. 

Q,  What  makes  these  fragments  red  hot  ? 

A  The  percussion  condenses  the  part 
gtruck ;  in  consequence  of  which,  some  of 
its  latent  heat  is  rendered  sensible,  and  ex- 
hil)its  Itself  in  these  red  hot  fragnifBnts, 


FIIICTION. 


165 


SECTION  II.  FRICTION. 

602. 

Q.  What  is  meant  hy  friction  ? 

A  The  act  of  rubbing  two  things  together  ; 
as  the  Indians  rub  two  pieces  of  icood  to- 
gether to  produce  fire. 

603 

Q.  How  do  the  Indians  produce  fire  hy 
merely  rubbing  two  pieces  of  dry  wood  to- 
gether ? 

A.  They  take  a  piece  of  dry  Avood,  sharp- 
ened to  a  point,  which  they  rub  quickly 
up  and  down  a  flat  piece,  till  a  groove  is 
made ;  and  the  dust  (collected  in  this 
groove)  catches  fire. 

60^. 

Q.  Why  does  the  dust  of  the  wood  catch 
fire  by  rubbing  ? 

A.  Because  latent  heat  is  developed  from 
the  wood  by  friction. 

The  best  woods  for  this  purpose  are  boxwood  against  mulberryy  or  laurel 
against  poplar  or  ivy 

605. 

Q.  Do  not  carriage  wheels  sometimes  catch 
fire? 

A.  Yes;  when  the  wheels  are  dry— or 
fit  too  tightly — or  revolve  very  rapidly. 

606. 

Q.  Why  do  wheels  catch  fire  in  such 
cases? 


1C6 


MECHANICAL  ACTION, 


A.  Because  the  friction  of  the  wheels 
against  the  axle-tree  disturbs  their  latent  heal, 
and  produces  ignition. 

607. 

Q.  What  is  the  use  of  greasing  cart 
wheels  ? 

A.  Grease  lessens  the  friction;  and,  be- 
cause there  is  less  friction,  the  latent  heat 
of  the  wheels  is  less  disturbed. 

608 

Q.  Why  does  rubbing  our  hands  and  faces 
make  them  feel  warm  ? 

A.  1st. — Because  friction  excites  the  la- 
tent  heat  of  our  hands  and  faces,  and  makes 
it  sensible  to  our  feeling :  and 

2nd. — The  blood  is  made  to  circulate  more 
quickly ;  in  consequence  of  which,  the  quan- 
tum of  heat  (left  in  its  passage)  is  increased. 

609. 

Q.  When  a  man  has  been  almost  drowned^ 
why  is  suspended  animation  restored  by  ruh- 
bing  ? 

A.  1st. — Because  friction  excites  the  la^ 
tent  heat  of  the  half-inanimate  body :  ind 

2nd. — It  makes  the  blood  circulate  more 
quickly y  which  increases  the  animal  heat. 

610. 

Q.  Why  do  two  pieces  of  ice  lubbed  to- 
gether m  elt  ? 


FRICTION. 


1G7 


A.  Ice  contains  140"*  of  latent  heat,  and 
(when  two  pieces  are  rubbed  together)  some 
of  this  latent  heat  is  made  sensible^  and 
melts  the  ice 

611. 

Q.  Are  not  forests  sometimes  set  on  fire 

by  friction  ? 

A.  Yes ;  when  two  branches  or  trunks 
of  trees  (blown  about  by  the  wind)  rub  vio^ 
lently  against  each  other ,  their  latent  heat  is 
developed,  and  sets  fire  to  the  forests. 

612. 

Q.  Why  do  carpenters'  tools  (such  as 
gimlets,  saws,  files,  etc.,)  become  hot  when 
used  ? 

A.  Because  the  friction  of  the  tools 
against  the  wood  disturbs  its  latent  heat, 
and  makes  it  sensible. 

613. 

Q.  Give  an  illustration  of  this  ? 

A.  When  cannon  is  bored,  the  borers 
become  so  intensely  hot  from  friction,  that 
rtioy  would  blister  the  hands,  if  touched. 

614. 

Q.  Why  do  these  borers  become  so  iu» 
tensely  hot  ? 

A.  Because  the  friction  of  the  borers 
against  the  metal  is  so  great,  that  it 
free  a  large  quantity  of  latent  heat. 


l08  MECHANICAL  ACTlOxV. 

SECTION   1/  I.  CONDENSATION  OR  COMPRESSION.* 

615. 

Q.  What  is  meant  by  compression  ? 

A.  The  act  of  bringing  parts  nearer  to- 
aether;  as  a  sponge  compressed  hy  hoiwg 
squeezed  in  the  hand. 

616. 

Q.  Cannot  heat  be  evolved  from  common 
air  merely  by  compression  ? 

A.  Yes ;  if  a  piece  of  German  tinder  be 
placed  at  the  bottom  of  a  glass  tube,  and  the 
air  in  the  tube  compressed  by  a  piston,  the 
tinder  will  catch  fire. 

In  a  common  syringe  or  squirt,  tho  handle  part  (which  contains  tht 
sucker,  and  is  forced  up  and  down)  is  called  "  the  Piston." 

617. 

Q.  ^¥h.y  will  the  tinder  catch  fire  ? 

A.  Because  the  air  is  compressed  ;  and  its 
latent  heat  being  squeezed  out,  sets  fire  to  the 
tinder  at  the  bottom  of  the  tube. 

618. 

Q.  When  an  air -gun  is  discharged  in  the 
dark,  why  is  it  accompanied  with  a  slight 
flash  ? 

A.  Because  the  air  is  very  rapidly  con- 

*  N.  B.  The  reduction  of  matter  into  a  smaller  compass  by  an  external 
or  mechanical  force  is  called  compression. 

The  reduction  of  matter  into  a  smaller  compass  by  some  internnl  ctctiom 
\JBiS  by  the  escape  of  caloric)  is  called  condensation. 


CONDENSATION  OR  COMPRESSION.  169 

densed,  and  its  latent  heat  developed  in  a 
fl>ash  of  light, 

N  B.  If  a  glass  lens  be  fixed  in  the  copper  ball,  (where  the  air  of  tha 
gun  is  condensed,)  a  flash  of  light  may  be  distinctly  discerned  at  the  stroke 
01  \he  piston. 

619. 

Q.  Why  do  detonating  salt  and  joowdor 
explode  on  being  rubbed  or  struck  ? 

A.  Because  the  mechanical  action  of 
nibbing  or  striking,  produces  sufficient  heat 
to  ignite  the  explosive  materials  of  which 
they  are  composed. 

620. 

Q.  Why  does  the  hole  made  by  a  shot  or 
cannon-ball  in  a  wall  or  timber,  look  as  if 
it  were  burnt  ? 

A.  Because  the  shot  or  cannon  balls  were 
so  heated  by  the  discharge,  as  actually  to 
scorch  the  material  into  which  they  pene- 
trated. 

62 1. 

Q.  Why  are  shot  and  cannon-balls  heated 
by  being  discharged  from  a  gun  or  cannon  ? 

A.  Because  the  air  is  so  rapidly  con- 
densed, when  the  discharge  is  made,  that 
sufficient  latent  heat  is  developed  to  make 
the  shot  or  balls  hot. 


15 


PART  IL 

NON-METALLIC  ELEMENTS. 


622. 

Q.  "What  is  meant  by  no7i-mefallic  eh 
meats  ? 

A.  Those  elementary  bodies  which  do 
not  belong  to  the  class  of  metals. 

Elementary  bodies  are  those  which  have  never  been  decomposed  ;  that 
is,  do  not  appear  to  be  composed  of  any  compounds,  bat  are  pure  sub- 
stances in  themselves.  At  present  there  are  reckoned  fifteen  non-metallio 
elementary  substances,  and  forty  which  belong  to  the  class  of  metals. 


CHAP.  L— OXYGEN  AND  OXIDES. 
623. 

Q.  What  is  the  difference  between  oxi/' 
gen.  and  an  oxide  ? 

A.  Oxygen  is  a  gas,  and  an  oxide  is  a  com- 
pound formed  by  the  union  of  oxygen  with 
ether  bodies. 

SECTION  I.  OXYGEN. 

624. 

Q.  What  is  oxijgen  ? 

A.  A  gaseous  hody:  which  is  found  largoljf 

170 


OXYGEN. 


171 


difiused  throughout  all  nature,  being  an  im- 
portant element  of  air  and  water,  rocks^ 
mrthsj  minerals y  etc. 

Oxygsn  gas  is  much  more  troublesome  to  make  than  hydrogen.  Tha 
eheap'sst  plan  is  to  put  a  few  ounces  of  manganese  (called  black  oxide  of 
manganese,)  into  an  iron  bottle,  furnished  with  a  bent  tube;  set  the  bottle 
OB  a  fire  till  it  becomes  red  hot,  and  put  the  end  of  the  tube  into  a  pan  of 
Water.  In  a  few  minutes,  bubbles  will  rise  through  the  water ;  these  bub- 
^les  are  oxygen  gas. 

The  bubbles  may  be  collected  thus  : — Fill  a  common  bottle  with  water ; 
Jsi'ld  it  inverted  over  the  bubbles  which  rise  through  the  pan,  but  be  sure 
the  mouth  of  the  bottle  be  held  in  the  water.  As  the  bubbles  rise  into  the 
bottle  the  water  will  run  out ;  and  when  all  the  water  has  run  out,  the 
bottle  will  be  full  of  gas.  Cork  the  bottle  while  the  mouth  remains  under 
loater  ;  set  the  bottle  on  its  base:  cover  the  cork  with  lard  or  wax,  and 
the  gas  will  keep  till  it  be  wantea. 

N.  B.  The  quickest  way  of  making  oxygen  gas,  is  to  rub  together  in  a 
mortar  half  an  ounce  of  oxide  of  copper,  and  half  an  ounce  of  chlorate  of 
potassa.  Put  the  mixture  into  a  common  oil  flask,  furnished  with  a  cork 
which  has  a  bent  tube  thrust  through  i";  Heat  the  bottom  of  the  flask 
over  a  candle  or  lamp :  and  when  the  mixture  is  red  hot,  oxygen  gas  will 
be  given  off.  Note. — the  tube  must  be  immersed  in  a  pan  of  water  and 
the  gas  collected  as  before. 

(Chloride  of  potassa  may  be  bought  at  any  chemist's,  and  oxide  of  cop- 
per may  be  procured  by  heating  a  sheet  of  copper  red  hot,  and  when  cool, 
striking  it  with  a  hammer ;  the  scales  that  peel  off  are  oxide  of  copper.) 

Experiment. — Put  a  piece  of  red  hot  charcoal  (fixed  to  a  bit  of  wire,) 
into  your  bottie  of  oxygen  gas;  and  it  will  throw  oat  most  dazzling 
bparks  of  light 

Blow  a  candle  out ;  and  while  the  wick  is  still  red,  hold  the  candle  (by  a 
piece  of  wire,)  in  the  bottle  of  oxygen  gas;  the  wick  will  instantly  ignite, 
and  burn  brilliantly. 

(Burning  sulphur  emits  a  blue  flame,  when  immersed  in  oxygen  gas.) 

625. 

Q.  "lYlien,  and  by  whom,  was  oxygen  dis^ 
covered  ? 

A.  It  was  discovered  in  1774,  by  Scheele, 
in  Sweden,  and  Dr.  Priestly,  in  England, 
independent  of  each  other.  They  dfjscribed 
it  under  different  names. 

626. 

Q.  Who  gave  it  the  name  of  oxygen ;  and 
what  is  the  signification  of  the  word  ? 


172  OXYGEN  AND  OXIDES. 

A.  Lavoisier  gave  it  the  name,  which  is 
derived  from  two  Greek  words  o^vg  (oxus' 
an  acid,  and  yevvaco  (gennao)  I  produce. 

This  name  was  given  to  it,  because  it  was  then  thoug:ht  to  be  tbe  soU 
acidifying  principle.  Modern  discoveries  have  rectified  this  error,  by 
proving  me  existence  of  acids  in  the  composition  of  which  there  if  nt 
oxygen. 

627. 

Q.  Is  oxygen  ever  found  in  a  liquid  or  solid 
Btate? 

A.  No :  when  pure,  it  is  only  known  in 
the  gaseous  state  ;  all  eflforts  to  reduce  it  to 
a  liquid  or  solid  condition  by  cold  or  pres- 
sure, have  completely  failed. 

628. 

Q,  Has  oxygen  any  taste  or  smell  ? 
A.  It  is  when  pure,  colorless,  tasteless,  and 
moderous, 

629. 

Q.  Of  what  use  is  oxygen  in  the  atmosphere? 
A.  It  sustains  animal  life,  and  supports 
combustion 

630. 

Q.  What  peculiar  property  does  oxygen 
possess  with  regard  to  light  ? 

A.  It  refracts  light  less  than  any  other 
known  body. 

631. 

Q.  Why  do  we  feel  braced  and  light-hearted 
on  a  fine  spring  or  frosty  moniing  ? 


OXYGEN. 


173 


A,  1st.— Because  there  is  7nore  oxygen  in 
the  air  on  a  fine  frosty  morning,  than  there 
is  on  a  wet  day ;  and 

2nd. — -A  brisk  and  frosty  air  has  a  ten- 
dency to  brace  the  nervous  system. 

632. 

Q.  Why  do  dogs  and  cats  (confined  to  a 
room)  feel  lazy  and  droiozyy  at  the  approach 
of  rain  ? 

A.  1st. — Because  the  air  does  not  con- 
tain its  full  proportion  of  oxygen  ;  and 

2nd. — The  damp  depresses  their  nervous 
system,  and  makes  them  drowsy, 

633. 

Q.  When  sheep  lie  under  a  hedge,  and 
seem  unwilling  to  go  to  pasture,  rain  is  at 
hand  ;  Explain  the  reason  of  this  ? 

A.  1st. — As  the  air  does  not  contain  its 
full  proportion  of  oxygen,  they  feel  uneasy ; 
and 

2nd. — As  the  damp  air  relaxes  their  ner- 
vous system,  they*  feel  listless  and  drowsy. 

634. 

Q.  Wiiy  do  horses  neigh,  cattle  low,  sheep 
bleat,  and  asses  bray,  at  the  approach  of 
rain? 

A.  1st. — As  the  air  does  not  contain  its 
15^ 


174 


OXYGEN  AND  OXIDES. 


full  proportion  of  oxygen,  they  feel  a  diffi- 
culty in  breathing  ;  and 

2nd. — As  damp  relaxes  their  nerves ,  they 
feel  languid  and  uneasy. 

635. 

Q.  Mention  some  other  animals ^  which  in- 
dicate the  approach  of  rain  in  a  similar  way? 

A.  When  pigs  squeak,  as  if  in  great  pain 
~  -frogs  croak  with  a  loud,  hoarse  noise — 
owls  screech — woodpeckers  cry — peacocks 
scream — guinea-fowls  squall — or  ducks  and 
geese  are  unusually  noisy,  rain  is  close  at 
hand. 

636. 

Q.  Why  do  candles  and  fires  burn  with  a 
bluer  flame  in  wet  weather  ? 

A.  Because  the  air  contains  less  oxygen  in 
wet  weather,  and,  therefore,  the  heat  of  the 
fire  is  less  intense.  The  flame  is  blue,  be- 
cause the  fuel  is  not  thoroughly  consumed. 

637. 

Q.  What  is  meant,  when  it  is  said,  that 
the  oxygen  of  the  air  ''supports  combustion?^' 

A.  It  means  this  :  It  is  the  oxygen  of  the 
air  which  makes  fuel  burn. 

638. 

Q.  How  does  the  oxygen  of  the  air  make 
fuel  burn  ? 


OXIDES. 


175 


A.  The  fuel  is  decomposed  (by  heat)  into 
hydrogen  and  carbon;  and  these  elements 
combining  with  the  oxygen  of  the  air  pro* 
duce  combustion. 

639. 

Q.  What  are  the  uses  of  the  oxygen  of 
the  air  ? 

A.  To  support  combustion  and  sustain  life. 

640. 

Q.  What  is  meant,  when  it  is  said,  that 
Dxygen    sustains  life?'^ 

A.  It  means  this :  If  a  person  could  not 
inhale  oxygen,  he  would  die. 

641. 

Q.  What  good  does  this  inspiration  of 
oxygen  do  ? 

A.  1st. — It  gives  vitality  to  the  blood : 
and 

2nd. — It  is  the  cause  of  animal  heat. 

SECTION  II.  OXIDES 

642. 

Q.  What  are  oxides  ? 

A.  The  compounds  formed  by  the  union 
of  oxygen  with  other  bodies,  bear  the  gene- 
ral  name  of  oxides. 

643. 

Q.  AVhat  is  rust  ? 


176 


OXYGEN  AND  OXIDES. 


A.  The  oxidation  of  iron  in  moist  air. 

"  OxidatioTij^^  impregnation  with  oxygen. 
644. 

Q.  Why  does  iron  rust  ? 

A  Because  water  is  decomposed  when  it 
comes  in  contact  with  the  surface  of  iron ; 
and  the  oxygen  of  the  water  combining  with 
iron,  produces  an  oxide,  which  is  generally 
called  rust. 

Water  is  composed  of  Oxygen  and  Hydrogen,  in  the  following  propoi- 
Hons :  8  lbs.  of  Oxygen,  and  1  lb.  of  Hydrogen=9  lbs.  of  waier. 

645. 

Q.  Why  does  air  rust  iron  ? 

,  A.  Because  the  oxygen  of  the  air  combines 
with  the  surface  of  the  metal,  and  produces 
oxide  of  iron ;  which  is  generally  called 
"  rust.'' 

An  oxide  of  iron,  copper,  etc.,  is  oxygen  in  combination  with  iron  cop« 
per,  etc. 

646. 

Q.  Does  iron  rust  in  dry  air  ? 
A.  No ;  iron  undergoes  no  change  in  dry 
air. 

647. 

Q.  Why  does  hot  iron  scale  and  peel  off, 
when  struck  with  a  hammer  ? 

A.  Because  the  oxygen  of  the  air  very 
readily  unites  with  the  surface  of  the  hot 
iron,  and  forms  a  metallic  oxide  (or  rust,) 
which  scales  off  when  struck  with  a  hnm 
mer. 


OXIDES. 


177 


648. 

Q.  Why  do  stoves  and  fire-irons  become 
rusty  in  rooms,  which  are  not  occupied  ? 

A.  Because  the  air  is  damp ;  and  moist 
ftir  oxidizes  iron  and  steel. 

Oxidizes,  that  is,  rusts 
649. 

Q.  In  what  part  of  the  year  is  it  most 
difficult  to  keep  stoves  and  fire-irons  bright  ? 
A.  In  autumn  and  winter, 

650. 

Q.  Why  is  it  more  difficult  to  keep  stoves 
and  fire-irons  bright  in  autumn  wadi  winter 
than  in  spring  and  summer  ? 

A.  Because  the  capacity  of  the  air  for 
holding  water  is  constantly  on  the  decrease, 
after  the  summer  is  over;  in  conse- 
quence of  which,  vapor  is  deposited  on 
everything  with  which  the  air  comes  in 
contact. 

651. 

Q.  Why  does  greasing  iron  prevent  its 
becoming  rusty  ? 

A.  Because  grease  prevents  the  humidity 
of  air  from  coming  in  contact  with  the  sur- 
face of  the  iron. 

652. 

Q.  Why  does  painting  iron  prevent  it  froin 
rusting  ? 


178 


OXYGEN  AND  OXIDES. 


A.  Because  paint  prevents  the  moist  air 
from  coming  in  contact  with  the  iron. 

653. 

Q.  Why  will  bright  iron  lose  its  polish  hy 
l)eing  put  into  a  fire  ? 

A.  Because  the  oxygen  of  the  air  very 
r-eaclily  unites  with  the  surface  of  hot  iron, 
and  forms  a  metallic  oxide;  which  displays 
itself,  in  this  case,  by  a  dull  leaden  color, 
instead  of  a  red  rust. 

654. 

Q.  Why  do  not  stoves  rust  so  frequently 
as  pokers  and  tongs  ^ 

A.  Because  stoves  are  generally  cohered 
with  plumbago,  or  black  lead. 

655. 

Q.  T^Tiat  is  plumbago,  or  black  lead  ? 
A.  A  mixture  of  charcoal  and  iron. 

Plumbago  (strictly  speaking)  is  a  chemical  union  of  carbon  and  iron,  io 
the  following  proportions : — 91  parts  carbon,  and  9  iron  But  the  EIACH 
LEAD  sold  in  shops  is  a  nnixiure  of  charcoal  and  iron  filings. 

N.  B.  A  most  excellent  varnish  to  prevent  rust  is  made  of  one  pint  of  fa( 
oil  varnish,  mixed  wMth  five  pints  of  highly  rectified  spirits  of  turpentine, 
rubbed  on  tlie  iron  or  steel  with  a  piece  of  sponge.  This  varnish  may  be 
upplied  to  bright  stoves,  and  even  mathematical  instruments,  wiihoul  ii> 
jurnig  their  delicate  polish. 

656. 

Q.  Why  does  ornamental  steel  (of  a  pur- 
ple or  lilac  color)  rust  more  readily  than 
polished  white  steel  ? 

A.  Because  the  lilac  tinge  is  produced  by 
'partial  oxidation ;  and  the  process  which 


OXIDES. 


179 


fuims  rusts,  has,  therefore,  already  com- 
menced, 

657. 

Q,  How  can  lilac  sImI  be  kept  free  from 
rust  ? 

A.  By  keepmg  it  in  a  very  dry  place. 

658. 

Q.  If  dry  air  contains  oxygen^  why  doea 
it  not  rust  iroriy  as  well  as  moist  air  ? 

A.  Because  moisture  is  always  needed, 
in  order  to  bring  into  action  the  affinity  of 
oxygen  for  steel. 

659. 

Q.  When  a  black  subsoil  is  dug  or  ploughed 
up,  it  turns  of  a  reddish  brown  color  after 
a  short  time ;  Why  is  this  ? 

A.  Because  the  soil  contained  a  certain 
compound  of  iron,  called  the  protoxide/' 
which  is  black.  This  protoxide  of  iron, 
absorbing  more  oxygen  from  the  moist  air, 
IS  converted  into  another  compound,  called 
the  *'per-oxide  of  iron,''  which  is  of  a  red- 
dish rusty  color. 

Tnere  are  Iwo  oxides  of  iron,  the  one  containing  more  oxygen  than  th« 
other  The  protoxide  which  contains  the  least  oxygen  is  black  ;  the  per- 
oxide.^ which  contains  the  most  oxygen  is  red, 

660. 

Q.  Do  any  other  metals  (besides  iron) 
combine  rapidly  with  oxygen  ? 


180 


OXYGEN  AND  OXIDES. 


A.  Yes;  copper,  lead,  mercury,  and  even 
isilver  to  some  extent. 

661. 

Q.  Why  does  copper  tarnish  ? 

A.  The  tarnish  of  copper  is  caused  by  its 
oxidation;  that  is,  the  oxygen  of  the  air 
combines  with  the  surface  of  the  copper, 
and,  (instead  of  rusting  it)  covers  it  with  a 
dark  tarnish. 

662. 

Q.  Why  does  lead  become  a  darker  hue, 
by  being  exposed  to  the  air  ? 

A.  Because  the  vapor  of  the  air  com- 
bines with  the  lead,  and  oxidizes  its  surface  ; 
but  instead  of  becoming  rusty,  the  surface 
assumes  a  darker  hue. 

663. 

Q.  Why  does  lead  lose  its  brightness,  and 
become  dull,  by  being  exposed  to  the  air  ? 

A.  The  dullness  of  the  lead  is  caused  by 
the  presence  of  a  carbonate  of  the  oxide. 
When  the  oxide  is  formed,  it  attracts  car- 
honic  acid  from  the  air,  and  (combining  with 
it)  produces  a  carbonate,  which  gives  the 
dull  tint  to  old  lead. 

664. 

Q.  Why  is  it  difficult  to  keep  silver  bright? 
A.  Because  the  vapor  of  the  air  oxidizefl 
its  surface,  and  farnishrs  it. 


OXIDES. 


181 


665. 

Q.  Why  does  salt  turn  silver  black? 

A.  Because  it  precipitates  an  oxide  of 
silver  on  the  surface  of  the  spoon,  the  color 
of  which  is  black. 

Marking  ink  "  is  made  of  soda  and  the  nitrate  of  silver  ;  the  bla3k 
tfi&rk  being  Que  to  the  oxide,  precipitated  on  the  cloth. 

666. 

Q  How  can  the  black  stain  of  silver^ 
made  by  salt  be  removed  ? 

A.  By  washing  the  silver  in  hartshorn 
or  common  ammonia;  by  which  means, 
the  oxide  will  be  re-dissolved,  and  the 
blackness  entirely  disappear. 

667. 

Q.  Why  do  silver  tea-pots  and  spoons  tar- 
nish more  quickly  than  bullion  ? 

A.  Because  alloy  of  some  baser  metal  is 
used,  to  make  them  more  hard  and  lasting  ; 
and  this  alloy  oxidizes  more  quickly  than 
silver  itself. 

668. 

Q.  Why  does  German  silver  turn  a  dingy 
yellow  in  a  few  hours  ? 

A.  Because  German  silver  has  a  great 
affinity  for  oxygen ;  and  shows  its  oxida- 
tion by  a  sickly  yellow  tarnish^  instead  of 
rust. 

16 


1S2  OXYGEN  AND  OXIDES. 

669. 

Q.  If  quicksilver  (or  mercury)  will  tar 
nish  like  copper  and  lead — why  does  it  pre- 
serve its  hrilliancy  in  barometers  and  thermo- 
meters ? 

A.  Because  the  air  is  excluded ;  and  no 
moisture  can  come  in  contact  with  it,  to 
oxidize  (or  tarnish)  it. 

670. 

Q.  Is  gold  affected  by  the  atmosphere  ? 

A.  Not  readily;  gold  will  never  com- 
bine with  oxygen  of  itself,  (that  is,  with- 
out aid.) 

671. 

Q.  Which  of  the  metals  is  capable  of  re 
sisting  oxidation  altogether  ? 

A.  Plat'inum  ;  in  consequence  of  which, 
the  graduated  arcs  of  delicate  "  instru 
ments-for-observation,"  are  made  of  plati- 
num instead  of  any  other  metal. 

672. 

Q  Why  is  platinum  used  for  the  gradu» 
ated  arcs  of  delicate  mathematical  instru- 
ments, instead  of  any  other  metal  ? 

A.  Because  it  will  never  oxidize ;  but 
retains  its  bright  surface  in  all  weathers,  free 
from  both  rust  and  tarnish. 


OXIDES.  183 
673. 

Q  For  what  other  scientific  purpose  is 
plat  mum  now  used? 

A.  For  crucibles  in  which  acids  are  em- 
ploj'ed  :  and  for  galvanic  batteries. 

674. 

Q.  Why  are  crucibles  (in  which  acids  are 
employed)  made  of  platinum  ? 

A.  Because  the  acid  would  act  upon  other 
metals,  or  upon  glass  ;  and  prevent  the  ex- 
perimenter's success. 

675. 

Q.  Before  platinum  was  discovered, 
which  of  the  metals  was  employed  for  the 
same  purpose  ? 

A.  Gold. 

Plat'innm  (a  white  metal,)  so  called  from  "  plata,"  the  Spanish  word 
fnT  silver.  It  was  introduced  from  South  America  into  England,  by  Mr. 
Wood,  ^A.  D.  1749.) 

676. 

Q.  Which  of  the  metals  have  the  greatest 
affinity  for  oxygen  ? 

A.  Those  called  potas'sium  and  so'dium. 

Potas'sium  and  so''dium  derive  their  names  from  potash  ai.d  soda.— 
Potas^sa  is  the  oxide  of  potas''ijium  ;  and  soda  is  the  oxide  of  so''diuni. 

677. 

Q.  How  is  the  affinity  of  potas'sium  and 
so'dium  for  oxygen  shown  ? 

A.  They  decompose  loater  as  soon  as  they 
are  brought  into  contact  with  it. 


184  HYDROGEN  AND  WATER. 


678. 

Q.  What  effect  has  potas'sium  on  water  ? 

A.  It  catches  fire  the  moment  it  is  thrown 
into  water,  and  bm-ns  with  a  vivid  flame 
which  is  still  further  increased  hy  the  00111- 
bustion  of  hydrogen^  separated  from  tlie 
water. 

N.  B.  Water  is  composed  of  oxygen  and  hydrogen ;  and  potas  siuai 
separates  the  two  gases. 

679. 

Q.  What  effect  has  so'dium  on  vmter  ? 
A.  It  does  not  take  fire  as  potas^sium 
does  ;  but  undergoes  very  rapid  oxidation. 


CHAP.  II.— HYDROGEN  AND  WATER. 

680. 

Q.  What  is  the  distinction  between  hy- 
drogen and  water  ? 

A.  Hydrogen  is  an  inflammable  ga^;  and 
water  is  composed  of  hydrogen  and  oxygen, 

SECTION  I.  HYDROGEN. 

681. 

Q.  What  is  hydrogen  ? 

A.  An  inflammable  gas.  The  gas  used 
in  our  streets  is  hydrogen  driven  out  of  zocl 


HYDROGEN.  185 

hy  heat.  Hydrogen  is  the  principal  ingre- 
dient of  water. 

Coal  ^as  (more  properly  speaking)  is  carburetted  hydrogen;  that  is  car- 
bon and  hydrogen. 

Hydrogen  derives  its  name  from  two  Greek  words  v6odp  udcr  (water,> 
I3>fi  Xnt  aa)  gennao  (I  produce.) 

682 

Q   When  was  hydrogen  gas  discovered  ? 
A.  After  the  middle  of  the  eighteenth 
century,  and  was  termed  inflammable  air. 

683. 

Q   Has  hydrogen  any  taste  or  color  ? 

A.  It  has,  when  pure,  neither  taste,  color 
nor  smell.  When  it  has  any  odor,  it  arises 
from  impurities. 

684. 

Q.  Does  hydrogen  support  life  ? 
A.  No ;  it  destroys  it,  rather  by  excluding 
oxygen  than  by  its  own  injurious  effects. 

685. 

Q.  Does  hydrogen  gas  like  oxygen  sup- 
port combustion  ? 
I  A.  No ;  it  is  highly  combustible,  but  does 

not  support  combustion  ;  uniting  with  oxy- 
gen  it  forms  water. 

686. 

Q.  What  are  the  peculiar  characteristics 
of  hydrogen  gas  ? 

A.  Lst. — It  is  the  lightest  of  all  known 
substances; 

16* 


186 


HYDROGEN  AND  WATER. 


2nd. — It  will  burn  immediately  on  being 
ignited ;  and 

3rd. — Alighted  candle  (immersed  in  this 
gas)  will  be. instantly  extinguished.* 

687. 

Q.  For  what  uses  are  hydrogen  gas  em- 
ployed ? 

A  1st. — Owing  to  its  levity  it  is  used  to 
inflate  balloons. 

2nd. — Burned  with  oxygen,  it  constitutes 
the  hydrogen  blowpipe  ;  and 

3rd.- — It  is  a  powerful  chemical  agent. 

Chemical  agent^^^  a  substance  employed  to  effect  chemical  changes. 
688. 

Q.  What  is  a  blow-ipiipe  ? 

A.  A  tube,  usually  bent  near  the  end, 
terminated  with  a  finely  pointed  nozzle,  for 
blowing  through  the  flame  of  a  lamp  or 
gas-jet;  and  producing  thereby  a  small 
conical  flame  possessing  very  intense  heat. 

689. 

Q.  Describe  the  hydrogen  blowpipe  ?  i 
A.  A  mixture  of  oxygen  and  hydrogen, 

*  Hydrogen  gas  may  be  made  thus : — Put  Fome  pieces  of  zinc  or  iron 
filings  into  a  glass  ;  pour  over  them  a  little  sulphuric  acid  (vitriol,)  diluted 
with  twice  the  quantity  of  water  ;  then  cover  the  glass  over  for  a  few 
minutes,  and  hydrogen  gas  will  be  given  off. 

Experiments. — If  a  flame  be  put  into  the  glass,  an  explosion  will  be 
ttiade. 

If  the  experiment  be  tried  in  a  phial,  which  has  a  piece  of  tobacco  p-pa 
.'un  through  the  cork,  and  a  light  held  a  few  moment*  to  the  top  of  the 
pipe,  a  flame  will  be  made. 

If  a  ialloon  be  held  over  the  phial  (so  that  the  gas  can  inflate  it,>  »hf 
balloon  will  ascend  in  a  very  few  minuses. 


WATER. 


187 


when  Ignited^  produces  an  intense  Keat,  and 
constitutes  the  hydrogen  blowpipe. 

690. 

Q.  Who  invented  the  hydrogen  blowpipe  ? 
A  Dr.  Hare,  of  Philadelphia. 

691. 

Q.  Can  you  describe  the  Drummond  light! 

A.  It  is  the  ignited  flame  of  a  mixture  of 
dxygen  and  hydrogen,  projected  against  lime  ; 
the  lime  becomes  intensely  luminous,  and 
forms  the  well  known  Drummond  light. 

SECTION  II.  ^WATER. 

\  692. 

Q.  What  is  water  ? 

A.  Water  is  a  fluid,  composed  of  oxygen 
and  hydrogen,  in  the  proportion  of  e^'glit 
parts  of  oxygen  to  one  part^of  hydrogen^^^ 

Q.  Why  is  water  fluid? 

A.  Because  its  particles  are  kept  separate 
by  latent  heat ;  when  a  certain  quantity  of 
this  latent  heat  is  driven  out  water  becomes 
solid,  and  is  called  ice. 

By  increasing  its  latent  heat,  the  particles  of  water  are  again  subd  ivule<| 
into  invisible  steam. 

694. 

Q.  Why  is  pump-water  called  ^'hard  wa^ 


188  IIYDIIOGEN  AND  WATER. 

A.  Because  it  is  laden  with  foreign  mat- 
ters, and  will  not  readily  dissolve  substances 
immersed  in  it. 

695. 

Q  What  makes  pump-water  hard  ? 

A.  When  it  filters  through  the  earthy 
it  becomes  impregnated  with  sulphate  of  lime ^ 
and  many  other  impurities  from  the  earths 
mid  minerals  with  which  it  comes  in  contact, 

696. 

Q.  What  is  the  cause  of  mineral  springs  ? 

A.  When  water  trickles  through  the 
ground,  it  dissolves  some  of  the  substances 
with  which  it  comes  in  contact ;  if  these 
substances  are  metallic,  the  water  will  par- 
take of  their  mineral  character. 

Some  water  is  imbued  with  Ume  ;  some  with  salt,  etc.,  etc. 

697. 

Q.  Why  is  it  difficult  to  wash  our  hands 
clean  with  hard  water  ? 

A.  Because  the  soda  of  the  soap  combines 
with  the  sulphuric  acid  of  the  hard  water — » 
and  the  oil  of  the  soap  with  the  lime — and 
floats  in  flakes  on  the  top  of  the  water, 

N  B  Sulphate  of  lime  consists  of  sulphuric  acid  and  lime. 

698. 

Q.  Why  is  it  difficult  to  wash  in  salt 
water  ? 


WATER. 


189 


A.  Because  it  contains  muriatic  acid;  and 
(lie  soda  of  soap  combines  with  the  muriatic 
acid  of  the  salt  watery  and  produces  a  cloudi- 
ness. 

699. 

Q.  What  is  the  cause  of  petrifactiom  ? 

A.  While  water  rolls  under  ground,  its 
impurities  are  held  in  solution  by  the  pre- 
sence of  carbonic  acid;  but  when  the  stieam 
reaches  the  open  air,  its  carbonic  acid 
escapes,  and  these  impurities  are  precipita- 
ted on  various  substances  lying  in  the  course 
of  the  stream. 

These  impurities  are  especially  carbonate  of  lime  and  iron. 
700. 

Q.  Why  does  water  clean  dirty  linen  ? 
A.  Because  it  dissolves  the  stains,  as  it 
would  dissolve  salt. 

701. 

Q.  Why  does  soap  greatly  increase  the 
cleansing  power  of  water  ? 

A.  Because  many  stains  are  of  a  greasy 
nature  ;  and  soap  has  the  power  of  uniting 
tvith  greasy  matters,  and  rendering  them 
soluble  in  water. 

702. 

Q.  Why  is  rain-wafer  soft  ? 
A.  Because  it  is  not  impregnated  with 
?arths  and  minerals. 


190  HYDROGEN  AND  WATER. 


703. 

Q.  Why  is  it  more  easy  to  wash  with  soft 
water,  than  with  hard  ? 

A.  Because  soft  water  unites  freely  with 
Boap,  and  dissolves  it;  instead  of  decomposing 
it,     hard  water  does. 

704. 

Q.  Why  do  wood  ashes  make  hard  water 
soft? 

A.  1st. — Because  the  carbonic  acid  of  wood 
ashes  combines  with  the  sulphate  of  lime  in  the 
hard  water,  and  converts  it  into  chalk  ;  and 

2nd. — Wood  ashes  convert  some  of  the 
sohible  salts  of  water  into  insoluble,  and 
throw  them  down  as  a  sediment ;  in  conse- 
quence of  which,  the  water  remains  more 
pure. 

705. 

Q.  Why  has  rain-water  such  an  unpleasant 
smell,  when  it  is  collected  in  a  rain-water 
tub  or  tank  ? 

A.  Because  it  is  impregnated  with  fig- 
composed  organic  matters,  washed  from  roofs, 
trees,  or  the  casks  in  which  it  is  collected. 

706. 

Q.  Why  does  melted  sugar  or  salt  give  a 
flavor  to  water  ? 
A.  Because  the  sugar  or  salt  (being  dis- 


WATER. 


191 


united  into  very  minute  particles)  floats 
about  the  water,  and  mixes  with  every  part. 

707. 

Q.  A¥hy  does  hot  water  melt  sugar  and 
salt  quicker  than  cold  water  ? 

A.  Because  the  heat  (entering  the  pores 
of  the  sugar  or  salt)  opens  a  passage  for  the 
water. 

708. 

Q.  Why  is  sea-water  brackish  ? 

A.  1st. — Because  the  sea  contains  mines 
of  salt  at  the  bottom  of  its  bed  ; 

2nd. — It  is  impregnated  Avith  bituminous 
matter,  which  is  brackish ;  and 

3rd. — It  contains  many  putrid  substances 
of  a  brackish  nature. 

709. 

Q.  lyiiy  is  not  rain-water  salt,  although 
most  of  it  is  evaporated  from  the  sea  ? 

A.  Because  salt  will  not  evaporate  ;  and, 
therefore,  when  sea-water  is  turned  into 
vapor,  its  salt  is  left  behind. 

710. 

Q.  Wliy  does  running  water  oscillate  and 
whirl  in  its  current  ? 

A.  1st. — Because  it  impinges  against  its 
hanks,  and  is  perpetually  diverted  from  its 
forward  motion ;  and 


102 


NITIIOGEN  AND  AIR. 


2n(l.  Ijecause  the  centre  of  a  river  llowy 
faster  tlian  its  sides. 

711. 

(}.  Why  do  the  sides  of  a  river  How  more 
tardily  than  its  centre  ? 

A.  Because  they  ruh  against  the  hanks, 
ttnd  are  delayed  in  their  current  by  this 
friction . 


CHAP  III.— NITROGEN  AND  AIR. 

SECTION  I.  NITROGEN. 

712. 

Q.  What  is  nitrogen  ? 

A.  An  invisible  gas  which  abounds  in 
animal  and  vegetable  substances  ;  The  fol- 
lowing are  its  peculiar  characteristics  : 

1st. — It  will  not  burn  ; 

2nd. — An  animal  cannot  live  in  it ; 

3rd. — It  is  the  principal  ingredient  in 
common  air.* 

Nearly  four  gallons  out  of  every  five  being  nitrogen  gas. 
Nitrogen,  that  is,  generator  of  nitre ;  also,  called  azou,  from  the  Greek 
words  a  (a)  privative,  or  to  deprive  of,  and  Wl  (zoe)  life. 

713. 

Q.  When  and  by  whom  was  nitrogen  dis- 
covered? 

*  Nitrogen  gas  may  easily  be  obtained  thus: — Put  a  piece  of  burning 
phosphorus  on  a  little  stand  in  a  plate  of  water ;  and  cover  a  bell  glass  over 
It.  (Be  sure  the  edge  of  the  glass  stands  m  f^e  trater.)  In  a  few  minutes 
the  oxygen  of  the  air  will  be  taken  up  by  the  burning  phosphorus ;  and 
nitrogen  alone  will  be  left  in  the  bell  gUss. 

N.  B.  The  white  fume  which  will  arise  and  be  absorbed  by  the  water  in 
this  experiment  is  phosphoric  acid ;  that  is,  phosphorus  cnmhinei  with 
ixygen  of  the  air. 


AIR. 


193 


A.  In  the  year  1772,  by  Rutherford. 

714. 

Q.  Is  nitrogen  capable  of  sustaining  com- 
hmtion  ? 

A.  No;  nitrogen,  like  hydrogen,  is  tn- 
capable  of  sustaining  combustion  or  animal 
existence,  although  it  has  no  positive  poison- 
ous properties. 

715. 

Q.  Has  nitrogen  any  color  1 
A.  No  ;  nitrogen  has  neither  color,  taste, 
nor  smell. 

SECTION  II.  AIR. 

716. 

Q.  What  are  the  elements  of  atmospheric 
air  ? 

A.  Oxygen  and  nitrogen  mixed  together 
in  the  following  proportions ;  four  gallons 
of  nitrogen  and  one  of  oxygen,  will  make 
five  gallons  of  common  air. 

717. 

Q.  Is  not  the  air  we  breathe  almost 
wholly  composed  of  nitrogen  ? 

A.  It  is ;  about  four- fifths  of  the  air  is 
nitrogen  and  the  other  one-fifth  is  oxygen. 

But  nitrogen  is  a  gas  which  cannot  support  animal  life— whereas,  tho 
nir  or  atmosphere  which  we  breaihe  is  a  thin  transparent  Jluid  which  eur- 
'oiinc'C'  the  earth,  and  xup-portf  nnimal  life  by  respiration 

^7 


194 


NITROGEN  AND  AIR. 


718. 

Q.  Why  is  there  so  much  nitrogen  in  th^'. 
air? 

A.  In  order  to  dilute  the  oxygen.  If  the 
oxygen  were  not  thus  diluted,  fires  would 
burn  out  too  quickly,  and  life  would  be  too 
rapidly  exhausted. 

719. 

Q.  Is  air  material^  that  is,  is  it  composed 
of  matter  ? 

A.  It  is ;  we  do  not  see  the  air  in  the 
room,  because  it  is  transparent ;  but  we  feel 
it  when  we  run  or  fan  ourselves,  and  we  hear 
through  the  medium  of  the  air ;  therefore, 
it  is  material,  or  composed  of  matter ;  for 
matter  is  that  which  is  perceived  by  our 
senses. 

720 

Q.  Is  air  invisible  ? 

A.  No ;  for  although  we  cannot  perceive 
it  immediately  around  us,  when  we  look  up 
into  the  firmament  illuminated  by  the  sun, 
the  air  appears  of  a  beautiful  azure.  This 
is  the  mass  of  the  atmosphere.  Distant 
mountains  appear  of  a  blue  color,  owing  to 
our  viewing  them  through  the  atmosphere. 

721. 

Q.  Why  can  we  not  see  the  air  imine* 


CARBON. 


195 


diately  around  us  of  the  samo  beautiful 
azure  ? 

A.  So  small  a  portion  of  air  reflects  little 
or  no  color,  while  a  mass  would  be  capable 
of  reflecting  a  beautiful  tint ;  so  it  is  with 
B.  small  quantity  of  sea-water  dipped  up  in 
a  glass ;  it  would  appear  perfectly  colorless, 
yet  the  deepest  part  of  the  ocean  appears 
of  a  dark  green,  approaching  to  a  black. 


CHAR  IV.— CARBON. 
722 

Q.  What  is  carbon  ? 

A.  A  solid  substance  generally  of  a  dark 
or  black  color,  well  known  under  the  forms 
of  charcoal,  lamp-black,  coke,  etc. 

723. 

Q.  Carbon  occurs  in  nature  crystallized  in 
two  forms ;  What  are  they  ? 
A.  The  Diamond  and  Graphite. 

Graphite.,  known  by  the  names  of  plumbago,  or  black>lead,  is  used  fOP 
making  pencils  for  drawing  and  writing. 

724. 

Q.  What  is  a  crystal? 

A.  The  geometrical  form  possessed  by  a 
vast  number  of  mineral  and  saline  substan- 
ces, whose  particles  combine  with  one  ano- 
ther by  the  attraction  of  cohesion,  accord- 
ing to  certain  laAVS,  the  investigation  of 


196 


CARBON. 


which  belong  more  properly  to  the  science 
of  crystallography. 

725. 

Q,  What  peculiar  properties  does  the  din 
mond  possess  ? 

A.  It  possesses  a  degree  of  hardnes^\ 
superior  to  that  of  any  other  mineral ;  it 
scratches  all  other  bodies  but  is  scratched 
by  none. 

It  acquires  positive  electricity  by  friction, 
but  does  not  retain  it  for  more  than  half  an 
hour. 

It  possesses  either  single  or  double  re- 
fraction according  to  its  crystalline  form. 

When  exposed  to  the  sun's  rays  for  a 
certain  time,  or  to  the  blue  rays  of  the 
prismatic  spectrum,  it  becomes  phospho- 
resc(  nt. 

(For  a  description  of  graphite^  see  under  metals.) 
726. 

Q.  Can  you  give  an  example  of  carbon 
in  its  uncrystdlized  state  ? 

A.  Lamp-black,  the  soot  produced  by  the 
imperfect  combustion  of  oil  or  resin,  is  pure 
carbon  in  its  uncrystallized  or  amorphous 
Btate. 

"  Amorphous  " — shapeleBs,  without  form. 
727. 

Q.  What  is  charcoal  ? 


CARBON. 


197 


A.  Wood  which  has  been  exposed  to  a 
red  heat  till  it  has  been  deprived  of  all  its 
gases  and  volatile  parts. 

728. 

Q.  Why  does  charcoal  remove  the  taint  of 
meat  ? 

A.  Because  it  absorbs  all  putrescent  effluvia^ 
whether  they  arise  from  animal  or  vegeta- 
l  le  matter. 

729. 

Q.  What  other  kinds  of  charcoal  are  there? 
A.  Cokey  the  charcoal  of  pit-coal,  and 
Anthracite y  which  is  a  mineral  charcoal. 

Anthracite  differs  from  pit-coal,  in  containing  no  bitumen,  and,  therd- 
fore,  burning  without  flame  or  smoke. 

730. 

Q.  Why  is  a  charcoal  fire  hotter  than  a 
wood  fire  ? 

A.  Because  charcoal  is  very  pure  carbon; 
and,  as  it  is  the  carbon  of  fuel  which  pro- 
duces the  glowing  heat  of  combustion, 
therefore,  the  purer  the  carbon,  the  more 
intense  will  the  heat  of  the  fire  be. 

731. 

Q.  Why  does  coal  make  such  excellent 
fuel? 

?    A.  Because  it  contains  a  large  amount  of 
carbon  and  hydrogen  gas,  in  a  very  compact 
Rnd  convenient  form. 
17* 


198  CARBON. 

732. 

Q.  Why  will  not  stones  do  for  fuel  as  well 

as  coal  ? 

A.  Because  they  contain  no  hydrogen  and 
little  or  no  carbon. 

733. 

Q.  Why  will  not  iron-cinders  bum  ? 

A .  Because  they  contain  impurities,  which 
are  not  so  ready  to  combine  with  oxygen, 
as  carbon  and  hydrogen  are. 

734. 

Q.  Of  what  are  oil,  tallow,  and  wax,  com- 
posed ? 

A.  Principally  of  carbon  and  hydrogen 
gas.  The  solid  part  is  carbon,  the  volatile 
part  is  hydrogen  gas. 

735. 

Q.  Why  arc  timbers  which  are  to  be  ex 
posed  to  damp  charred  ? 

A.  Because  charcoal  undergoes  no  change 
by  exposure  to  air  and  water;  in  conse- 
quence of  which,  timber  will  resist  weather 
much  longer  after  it  has  been  charred. 

736. 

Q.  Why  should  sick  persons  eat  dry  foasfj  - 
rather  than  bread  and  butter  ? 

A.  Because  the  charcoal  surface  of  the 


CARBON. 


199 


toast  helps  to  absorb  the  acids  and  impuri- 
ties  of  a  sick  stomach. 

There  are  other  reasons  which  belong  lo  the  science  of  med.cine. 
737. 

Q.  Why  should  toast  and  water  intendal 
for  the  sick  be  made  of  burnt  bread  ? 

A.  Because  the  charcoal  surface  of  burnt 
bread  prevents  the  water  from  being  af- 
fected by  the  impurities  of  the  sick  room. 

73S, 

Q.  Why  does  a  piece  of  burnt  bi^ead  make 
impure  water  fit  to  drink  ? 

A.  Because  the  surface  of  the  bread 
(which  has  been  reduced  to  charcoal  by  be- 
ing burnt,)  absorbs  the  impurities  of  the  loa,- 
ter,  and  makes  it  palatable. 

739, 

Q.  Why  are  water  and  wine  casks  charred 
inside  ? 

A.  Because  charring  the  inside  of  a  cask 
reduces  it  to  a  kind  of  charcoal ;  and  char- 
coal (by  absorbing  animal  and  vegetable 
impurities,)  keeps  the  liquor  sweet  and 
good. 

740. 

Q.  Why  is  water  purified  by  being  filtered 
through  charcoal  ? 

A,  Because  charcoal  absorbs  the  impuri* 


200 


CARBON. 


ties  of  the  water,  and  removes  all  disagree- 
able tastes  and  smells,  whether  they  arise 
from  animal  or  vegetable  matter. 

SECTION  I.  CARBONIC  ACID. 

741. 

Q.  What  is  carbonic  acid  gas? 
A.  A  gas  formed  by  the  union  of  carbon 
and  oxygen  ;  it  used  to  be  called  fixed  air. 

3  lbs.  of  carbon  and  8  lbs.  of  oxygen  will  form  11  lbs.  of  carbonic  acid. 
742. 

Q.  What  gas  is  generated  by  a  lighted 
candle  or  lamp  ? 

A.  Carbonic  acid  gas, — formed  by  the 
union  of  the  carbon  of  the  oil  or  tallow  with 
the  oxygen  of  the  air. 

743. 

Q.  Under  what  circumstances  does  carbon 
most  readily  unite  with  oxygen  ? 

A.  1st. — When  its  temperature  is  raised  : 
Thus  if  carbon  be  red  hot,  oxygen  will  most 
readily  unite  with  it :  and 

2nd. — ^When  it  forms  part  of  the  fluid 
blood. 

744. 

Q.  Why  do  oxygen  and  carbon  so  rea- 
dily unite  in  the  blood  ? 

A  Because  the  atoms  of  carbon  are  so 


CARBONIC  ACm. 


201 


looseh/  attracted  by  the  other  materials  of  the 
blood,  that  they  unite  very  readily  with  the 
oxygen  of  the  air  inhaled, 

745. 

Q  Is  carbonic  acid  whoksome 

A.  No ;  it  is  fatal  to  animal  life  :  and 
(whenever  it  is  inhaled)  acts  like  a  narcotic 
poison — producing  drowsiness,  v/hich,  some- 
times ends  in  death. 

746 

Q.  How  can  any  one  know,  if  a  place  be 
infested  with  carbonic  acid  gas  ? 

A.  If  a  pit  or  well  contain  carbonic  acid, 
a  candle  (let  down  into  it)  will  be  instantly 
extinguished.  The  rule,  therefore,  is  this — • 
where  a  candle  will  burn,  a  man  can  live  ;  but 
what  will  extinguish  a  candle,  will  also  destroy 
life. 

Q.  Why  does  a  miner  lower  a  candle  into 
a  mine,  before  he  descends  ? 

A.  Because  the  candle  will  be  extinguished 
if  the  mine  contains  carbonic  acid  gas :  but 
if  the  candle  is  not  extinguished,  the  mine  is 
mfe^  and  the  man  may  fearlessly  descend. 

748 

Q.  Why  does  a  crowded  room  produce 
head'-ache  ? 


202 


CARBON. 


A.  Because  we  breathe  air  vitiated  hy 
the  crowd. 

749. 

Q.  Why  is  the  air  of  a  room  vitiated  by 
9  rowd? 

A  Because  it  is  deprived  of  its  due  pro- 
portijn  of  oxygen  and  laden  with  carbonic 
ncid. 

750. 

Q.  How  is  the  air  of  a  room  aflected 
thus  by  a  crowd  ? 

A.  The  elements  of  the  air  inhaled  are 
separated  in  the  lungs : — the  oxygen  is  con- 
verted in  the  blood  into  carbonic  acid  ;  and 
the  carbonic  acid  (together  with  the  nitro- 
gen) is  thrown  back  again  by  the  breath 
into  the  room. 

751 

Q.  Is  all  the  nitrogen  rejected  by  tho 
lungs  ? 

A.  Yes ;  all  the  nitrogen  of  the  air  is 
always  expired. 

752, 

Q.  Why  is  a  crowded  room  unwholesome  1 
A.  Because  the  oxygen  of  the  air  is  oh- 
sorbed  by  the  lungs  ;  and  carbonic  acid  gas 
(which  is  a  noxious  poison)  is  substituted 
for  it. 


CARBONIC  ACID. 


203 


753. 

Q.  Mention  the  historical  circumstances, 
BO  well  known  in  connection  with  the 

Black  Hole  of  Calcutta:' 

A.  In  the  reign  of  Greorge  II.,  the  Raja 
(or  Prince)  of  Bengal,*  inarched  suddenly 
to  Calcutta,  to  drive  the  English  from  the 
country;  as  the  attack  was  unexjDected,  the 
English  were  obliged  to  submit,  and  one 
hundred  and  forty-six  persons  were  taken 
prisoners. 

754. 

Q.  What  became  of  these  prisoners  ? 

A.  They  were  driven  into  a  place  about 
eighteen  feet  square,  and  fifteen  or  sixteen 
feet  in  height,  with  only  two  small  grated 
windows.  One  hundred  and  tw^enty- three 
of  the  prisoners  died  in  one  night;  and  (of 
the  twenty-three  who  survived)  the  larger 
portion  died  of  putrid  fevers,  after  they 
were  liberated. 

755. 

Q.  Why  were  they  suffocated  in  a  few 
hours,  from  confinement  in  .this  close,  hot 
imso7i'hole  ? 

A.  Because  the  oxygen  of  the  air  ^vas 
soon  consumed  by  so  many  lungs,  and  its 

*  The  Sur  Raja,  at  Dowlat ;  a  young:  mun  of  violent  passions,  who  Karf 
but  just  sueceeded  to  the  throne  A.  P.  1758. 


204 


place  supplied  by  carbonic  acid,  exhaled  bj 
the  hot  breath. 

756 

Q.  Why  did  the  captives  in  the  black  koh 
die  sleeping? 

A.  1st. — ^Because  the  absence  of  oxygen 
quickly  affects  the  vital  functions,  depresses 
the  nervous  energies,  and  produces  a  lassi- 
tude which  ends  in  death ;  and 

2nd. — Carbonic  acid  gas  (being  a  narcotic 
poison)  produces  drowsiness  and  death,  in 
those  who  inhale  it. 

757 

Q.  Why  are  the  jungles  of  Java  and  Hin- 
dostan  so  fatal  to  life  ? 

A.  Because  vast  quantities  of  carbonic  acid 
are  thrown  off  by  decaying  vegetables  in 
these  jungles;  and  (as  the  wind  cannot 
penetrate  the  thick  brushwood  to  blow  the 
pernicious  gas  away)  it  settles  there,  and  de- 
stroys animal  life.- 

758. 

Q.  Why  do  persons  in  a  crowded  church 
feel  drowsy? 

A.  1st. — Because  the  crowded  congrega- 
tion inhale  a  large  portion  of  the  oxygen  of 
the  air,  which  alone  can  sustain  vit^ality 
and  healthy  action  :  and 


CARBONIC  ACID. 


205 


2n(i. — The  air  of  the  church  is  impreg- 
nated with  carbonic  acid  gas,  which  (being 
a  strong  narcotic)  produces  drowsiness  in 
those  who  inhale  it. 

759. 

Q.  Why  do  persons  who  are  much  in  the 
open  ail  enjoy  the  best  health  ? 

A ,  Because  the  air  they  inhale  is  much 
more  pure. 

760. 

Q.  Why  is  country  air  more  pure  than  the 
air  in  cities  ? 

A.  1st. — Because  there  are  fewer  inhabi- 
tants to  vitiate  the  air : 

2nd. — There  are  more  trees  to  restore 
the  equilibrium  of  the  vitiated  air :  and 

3rd. — ^The  free  circulation  of  air  keeps 
it  pure  and  wholesome :  (in  the  same  way 
as  running  streams  are  pure  and  whole- 
some, while  stagnant  waters  are  the  con- 
trary.) 

761. 

Q.  Why  does  the  scantiness  of  a  country 
population  render  the  country  air  more  pure? 

k.  Because  the  fewer  the  inhabitant;^  the 
less  carbonic  acid  will  be  exhaled ;  and  thus 
country  people  inhale  pure  oxy^m,  inste.'uj 
18 


20G 


CARBON. 


of  air  impregnated  with  the  narcotic  poison, 
called  carbonic  acid  gas. 

762. 

Q.  Why  do  trees  and  flowers  help  to  make 
country  air  wholesome  ? 

A.  1st. — Because  trees  and  flowers  ab- 
sorb the  carbonic  acid,  generated  by  the  lungs 
of  animals,  putrid  substances,  and  other  ob- 
noxious exhalations :  and 

2nd. — Trees  and  flowers  restore  to  the 
air  the  oxygen,  which  man  and  other  ani- 
mals inhale. 

763. 

Q.  Why  is  the  air  of  cities  less  whole- 
some, than  country  air  ? 

A.  1st. — Because  there  are  more  inhabi- 
tants to  vitiate  the  air : 

2nd. — The  sewers,  drains,  bins,  and  filth 
of  a  city,  very  greatly  vitiate  the  air : 

3rd. — The  streets  and  alleys  prevent  a 
free  circulation :  and 

4th. — There  are  fewer  trees  to  absorb 
the  excess  of  carbonic  acid  gas  and  restore 
the  equilibrium. 

764. 

Q.  Why  are  persons,  who  live  in  close 
rooms  and  crowded  cities,  generally  sickly  ? 
A.  Because  the  air  they  breathe  is  not 


CARBONIC  ACID. 


207 


pure,  but  is  (in  the  1st  place)  defective  in 
oxygen;  and  (in  the  2nd)  is  impregnated 
with  carbonic  acid  gas. 

765. 

Q.  Where  does  the  carbonic  acid  of  close 
rooms  and  cities  come  from  ? 

A.  From  the  lungs  of  the  inhabitants, 
the  sewers,  drains,  and  other  like  places,  in 
which  organic  substances  are  undergoing 
decomposition. 

766. 

Q,  What  becomes  of  the  carbonic  acid  of 
crowded  cities  ? 

A.  Some  of  it  is  absorbed  by  vegetables ; 
and  the  rest  is  blown  away  by  the  wind,  and 
diffused  through  the  whole  volume  of  the 
air. 

767. 

Q.  Does  not  this  constant  diffusion  of 
carbonic  acid  affect  the  purity  of  the  whole 
air  ? 

A.  No  ;  because  it  is  wafted  by  the  win  J 
from  place  to  place,  and  absorbed  in  its  pas 
sage  by  the  vegetable  world. 

763. 

Q.  What  is  choke  damp  ? 

A.  Carbonic  acid  gas  accumulated  at  the 


208 


CARBON. 


bottom  of  wells  and  pits,  which  renders 
them  noxious,  and  often  fatal  to  life. 

769. 

Q.  Why  is  not  this  carbonic  acid  taken 
up  by  the  air  and  diffused,  as  it  is  in  cities  ? 

A.  Because  (being  heavier  than  common 
air)  it  cannot  rise  from  the  well  or  pit:  and 
no  wind  can  get  to  it,  to  blow  it  away. 

770. 

Q.  Why  are  persons  sometimes  killed  by 
leaning  over  beer  vats? 

A.  Because  vats  (where  beer  has  been 
made)  contain  a  large  quantity  of  carbonic  acid 
gas,  produced  by  the  ''vinous  fermentation'* 
of  the  beer ;  and  when  a  man  incautiously 
leans  over  a  beer  vat,  and  inhales  the  car- 
bonic acid,  he  is  immediately  killed  thereby. 

771. 

Q.  Why  are  persons  often  killed,  who  en- 
ter beer  vats  to  clean  them? 

A.  Because  carbonic  acid  (being  heavier 
than  atmospheric  air)  often  rests  upon  the 
bottom  of  a  vat:  when,  therefore,  a  person 
enters  the  vat,  and  stoops  to  clean  the  bottom^ 
he  inhales  the  pernicious  gas,  which  kills 
him. 

772. 

Q.  Why  are  persons  sometimes  killed  by 
having  a  charcoal  fire  in  their  bed-rooms  ? 


CARBONIC  ACID. 


209 


A.  Because  the  carbon  of  the  burning  char- 
coal unites  with  the  oxygen  of  the  air,  and 
forms  carbonic  acid  gas,  which  is  a  narcotic 
poison. 

773. 

Q.  If  carbonic  acid  settles  at  the  bottom 
of  a  room,  how  can  it  injure  a  person  lying 
on  a  bed,  raised  considerably  above  the  floor? 

A.  Because  all  gases  diffuse  themselves 
through  each  other,  as  a  drop  of  ink  would 
diffuse  itself  through  a  cup  of  water.  If, 
therefore,  a  person  slept  for  six  or  eight 
hours  in  a  room  containing  carbonic  acid, 
quite  enough  of  the  gas  will  be  diffused 
throughout  the  room  to  produce  death. 

The  heat  of  the  fire  assists  the  process  of  diffusione 
774. 

Q.  What  are  the  chief  sources  of  carbonic 
acid  ? 

A.  1st. — The  breath  of  animals. 

2nd. — The  decomposition  of  vegetable 
and  animal  matter. 

3rd. — Lime-stone,  chalk,  and  all  calca- 
reous stones, — in  which  it  exists  in  a  solid 
form. 

775. 

Q.  From  which  of  these  sources  is  carbo- 
nic  acid  most  likely  to  accumidate  to  a  noxious 
extent  ? 

18* 


210  CARBON. 

A.  From  the  fermentation  and  putrefac- 
tion of  decaying  vegetable  and  animal  mat- 
ters. 

776. 

Q.  How  can  this  accumulation  of  carbonic 
acid  be  prevented  ? 

A.  By  throwing  quick-lime  into  places, 
where  such  fermention  and  putrefaction  are 
going  on. 

777. 

Q.  How  will  quick-lime  prevent  the  accu- 
mulation of  carbonic  acid  ? 

A.  Quick-lime  will  absorb  the  carbonic 
acid;  and  produce  a  combination  called 
"  carbonate  of  lime.'^ 

778. 

Q.  Does  not  heavy  rain  as  well  as  quick- 
lime, prevent  the  accumulation  of  carbonic 
acid  ? 

A.  Yes;  an  abundant  supply  of  water  will 
prevent  the  accumulation  of  carbonic  acid, 
by  dissolving  it. 

N.  B.  Red  heat  (as  a  pan  of  red  hot  coals,  or  a  piece  of  red  hot  iron/ 
will  soon  absorb  the  carbonic  acid  gas,  accumulated  in  a  pit  or  well. 

779. 

Q.  What  effect  has  carbonic  acid  on  the 
water  in  which  it  is  dissolved  ? 

A.  It  renders  it  slightly  acid  to  the  tasto. 


CARBONIC  ACID.  211 
780. 

Q.  Why  does  gunpowder  explode  ? 

A,  Because  of  the  instantaneous  produc- 
tion and  expansion  of  carbonic  acid,  sulphur- 
ous acid,  and  nitrogen. 

Gunpowder  consists  of  76  parts  of  nitre,  13  of  charcoal,  and  11  of  sai 
phur. 

781. 

Q.  Why  is  boiled  water  flat  and  insipid  ? 

A.  Because  the  whole  of  the  carbonic  acid 
is  expelled  by  boiling,  and  escapes  into  the 
air. 

782. 

Q.  Why  does  fresh  spring  water  sparkle^ 
when  poured  from  one  vessel  to  another  ? 

Ao  Because  fresh  spring  and  pump  war 
ter  contain  carbonic  acid  ;  and  it  is  the  pre 
sence  of  this  gas  which  makes  the  watc 
sparkle. 

Much  of  the  froth  and  bubbling  of  ale,  beer,  water,  etc.,  when  the) 
are  "  poured  high,"  is  due  to  simple  mechanical  action. 

783. 

Q.  Why  is  beer  flat  if  the  cask  be  left  open 
too  long  ? 

A.  Because  too  much  of  the  carbonic  acid 
gas  (produced  by  fermentation)  is  suffered  to 
escape. 

784. 

Q.  Wliy  are  beer  and  porter  made  stale  by 
being  exposed  to  the  air  ? 


212 


CARBON. 


A.  Because  too  much  of  the  carbonic  acid 
gas  (produced  by  fermentation)  is  suflfered  tc 
escape. 

785. 

Q.  Why  does  beer  turn  flat  if  the  vent  peg 
be  left  out  of  the  tub  ? 

A.  Because  the  carbonic  acid  gas  escapes 
through  the  vent  hole. 

786. 

Q.  Why  does  saUceratus  make  cakes  light, 
particularly  if  they  are  mixed  with  sour 
milk? 

A.  Because  the  acid  of  the  milk  disen- 
gages the  carbonic  acid  contained  in  the  sal- 
seratus. 

787. 

Q.  Why  does  wood  decay  ? 

A.  Because  the  oxygen  of  the  air  unites 
with  the  carbon  and  hydrogen  of  the  wood, 
and  forms  carbonic  acid  and  water. 

788. 

Q.  Why  do  persons  throw  lime  into  bins 
and  sewersy  to  prevent  their  offensive  smell, 
in  summer  time  ? 

A.  Because  they  contain  large  quantities 
of  carbonic  acid  gas,  which  readily  combines 
with  lime  ;  and  producing  carbonate  of  limtj' 
neutralizes  the  offensive  gases. 


CARBONIC  ACID. 


213 


789. 

Q.  Why  is  quick-lime  formed  hy  buniiiig 
limestone  in  a  kiln? 

A.  Because  the  carbonic  acid  (which  ren 
dered  it  mild)  is  driven  off  by  the  heat  of 
the  kiln;  and  the  lime  becomes  gxiich  or 
caustic 

790. 

Q.  What  is  mortar  ? 

A.  Quick-lime  mixed  with  sand  and 
water. 

791. 

Q.  Why  does  mortar  become  hard  after  a 
few  days  ? 

A.  Because  the  lime  re-imbibes  from  the 
air  the  carbonic  acid  w^hich  had  been  expelled 
by  fire  ;  and  the  loose  powder  again  becomes 
as  hard  as  the  original  lime-stone. 

792. 

Q.  Explain  in  what  way  mortar  is  ad- 
hesive ? 

A.  When  the  carbonic  acid  is  expelled 
the  hard  lime-stone  is  converted  into  quick- 
lime^ which,  (being  mixed  with  sand  and 
water)  becomes  a  soft  and  sticky  plaster ;  but 
as  soon  as  it  is  placed  between  bricks,  it  m- 
bibes  carbonic  acid  again y  and  hardens  into 
lime-stone. 


214 


CARBON. 


793. 

Q.  Wherein  does  lime-stone  differ  in  ap- 
pearance from  quick-lime  ? 

A.  Lime-stone  is  a  hard,  rocky  substance  ; 
but  quick-lime  is  friable. 

794. 

Q.  How  is  the  carbonic  acid  of  water  pro 
duced  ? 

A.  From  the  presence  of  lime,  which  is 
frequently  held  in  solution  by  hard  water ; 
when  the  carbonic  acid  escapes  by  exposure 
to  the  air,  the  lime  is  deposited  as  a  carbonate, 

795. 

Q.  Why  is  hard  water  more  agreeable  to 
dririk  than  soft  water  ? 

A.  Chiefly  because  it  contains  carbonic 
acid. 

796. 

Q.  Why  is  water  fresh  from  the  pump 
more  sparkling  than  after  it  has  been  drawi? 
some  time. 

A.  Because  water  fresh  from  the  pump 
contains  carbonic  acid,  which  soon  esc-apes 
into  the  air,  and  leaves  the  water  flat  and 
stale. 

797. 

Q.  Why  should  hard  water  (used  for  wash 
ing)  be  expoped  to  the  air  ? 


CARBONIC  ACID. 


21b 


A.  Because  it  is  made  more  soft  by  ex- 
posure  to  the  aii. 

Most  spring  water  holds  lime  in  solution  as  a  bicarbonate,  in  conscq'^enco 
of  the  presence  of  abundant  carbonic  acid.  Carbonic  acid  escapes  by  ex- 
posure to  air — and  the  lime  is,  consequently  deposited  as  a  carbonate. 

798. 

Q.  Why  is  hard  water  made  more  soft  by 
exposure  to  the  air  ? 

A.  1st. — Because  the  mineral  salts 
(which  cause  its  hardness)  suhsida  ;  and 

2nd. — Because  the  carbonic  acid  of  the  wa- 
ter makes  its  escape  into  the  air. 

799. 

Q.  What  is  choke-damp  ? 

A.  Carbonic  acid  gas  accumulated  at  the 
bottom  of  wells  and  pits.  It  is  called  choke 
damp,  because  it  chokes  (or  suffocates)  every 
animal  that  attempts  to  inhale  it. 

It  suffocates  without  getting  into  the  lungSj  by  closing  the  ouier  orifice 
spasmodically. 

800. 

Q.  Why  are  rotting  leaves  hot? 

A.  Because  the  fermentation  of  rotting 
leaves  produces  carbonic  acid  gas,  which  pro* 
duction  is  always  attended  with  heat.  In 
fact,  rotting  is  a  species  of  slow  combustion. 

N.  B.  The  carbim  of  the  leaves  unites  with  the  oxygen  ol  the  air  to  pro- 
dace  carbonic  acid  gas,  and  the  new  combinations  disturb  latent  he^t,  and 
make  it  g^r.aible. 


216 


CARBON. 


§ — Effervescence . 
801, 

Q  From  what  is  the  word  effervesence  de^ 
rived  ? 

A.  From  the  Latin  word  effervesco  (to 
boil.) 

802. 

Q.  Can  the  capacity  of  water  for  dissolv- 
ing carbonic  acid  be  increased  ? 

A.  Yes.  Carbonic  acid  may  be  forced 
into  water  by  pressure  to  a  considerable  ex- 
tent. 

803. 

Q.  To  what  practical  uses  has  this  capa- 
city of  water  (for  dissolving  carbonic  acid) 
been  applied? 

A.  Effervescing  draughts  are  made  upon 
this  principle. 

804. 

Q.  Explain  the  cause  of  effervescence  in 
these  beverages  ? 

A.  The  carbonic  acid  of  the  beverage 
(being  prevented  by  the  cork  from  escaping) 
is  forced  into  the  liquor  by  pressure,  and  ab- 
sorbed by  it ;  but  when  the  cork  (or  pres- 
sure) is  removed,  some  of  the  carbonic  acid 
flies  off  in  bubbles  or  effervescence. 


EFFERVESCENCE. 


217 


805. 

Q.  Why  does  aerated  water  effervesce 
when  the  cork  is  removed  ? 

A.  While  the  bottle  remains  corked,  car- 
bonic acid  is  forced  into  the  water  by  pres- 
sure, and  absorbed  by  it;  but,  when  the 
cork  {or  pressure)  is  removed,  some  of  the 
(carbonic  acid  flies  off  in  effervescence. 

806. 

Q.  Why  does  soda  water  effervesce  ? 

A.  In  soda  water  there  is  forced  eight 
times  its  own  bulk  of  carbonic  acid  gas, 
which  makes  its  escape  in  effervescence,  as 
soon  as  the  cork  is  removed. 

807. 

Q.  Why  does  ginger  pop  fly  about  in  froth, 
when  the  string  of  the  cork  is  cut  ? 

A.  Because  it  contains  carbonic  acid  gas. 
While  the  cork  is  fast,  the  carbonic  acid  is 
forced  info  the  liquor ;  but  when  the  pressure 
is  removed  the  gas  is  given  off  in  effervescence. 

N.  B.  All  vinous  fermentation  produces  carbonic  acid.. 
808. 

Q.  Why  does  bottled  ale  froth  more  than 
draught  ale  ? 

A.  Because  the  pressure  is  greater  in  a 
bottle  than  in  a  tub  which  is  continually 
19 


218 


CARBON* 


tapped ;   and  effervescence  is  always  in 
creased  hy  pressure. 

809. 

Q,  What  produces  the  froth  of  hottlei 
porter  ? 

A.  Carbonic  acid  generated  by  the  vinoitn 
fermentation  of  the  porter :  This  gas  is  ab- 
sorbed by  the  liquor ^  so  long  as  the  bottle  is 
well  corked  ;  but  is  given  off  in  froth,  when 
the  pressure  of  the  cork  is  removed. 

810. 

Q.  What  gives  the  pleasant  acid  taste  to 
soda  water,  ginger  beer,  champagne,  and 
cider  ? 

A.  The  presence  of  carbonic  acid,  gene- 
rated by  fermentation ;  and  liberated  by 
effervescence,  when  the  pressure  of  the  cork 
is  removed. 

811. 

Q.  Why  does  the  effervescence  of  soda  wa- 
rer  and  ginger  beer  so  soon  go  off? 

A.  Because  the  carbonic  acid  (which  pro- 
duced the  effervescence)  very  rapidly  es- 
r-apes  into  the  air. 

812. 

Q.  Why  does  the  cork  of  a  champagne 
bottle  fly  off  the  instant  it  has  been  loosened 
from  the  neck  of  the  bottle  ? 


EFFERVESCENCE. 


219 


A.  Because  the  vast  quantity  ot  carbonic 
acid  gas  contained  in  the  liquor  can  no  longer 
be  confined  ;  and,  seeking  to  escape,  drives 
out  the  cork  with  great  violence , 

813. 

Q.  When  the  cork  of  a  champagne  or  soda 
water  bottle  is  drawn,  why  is  a  loud  report 
made? 

A.  Because  champagne  and  soda  water 
both  contain  a  great  amount  of  carbonic  acid 
gas;  which,  being  suddenly  liberated,  strikes 
against  the  air,  and  produces  the  report. 

814. 

Q.  Why  does  hartshorn  take  out  the  red 
spot  in  cloth,  produced  by  any  acid  ? 

A.  Because  hartshorn  is  an  alkali;  and 
the  peculiar  property  of  every  alkali  is  to 
neutralize  acids. 

SodT,  pota?h,  magfnesin,  etc  ,  are  alkalies. 

Upon  this  principle  effervescing  drinks  are  made  of  carbonate  of  soda 
(an  alkali)  and  citric  or  tartaric  acid.  Effervescence  is  produced,  by  th* 
giving  off  of  carbonic  acid  during  the  process  of  neutralization. 

N.  B.  The  carbonic  acid  is  formed  by  the  carbon  (of  the  carbonate  o* 
•oda)  combining  with  the  oxygen  of  the  acid. 

815. 

Q.  What  is  an  alkali  ? 

A.  The  converse  of  an  acid ;  as  bitter  is 
the  converse  of  sweet ,  or  insipid  the  converse 
of  pungent. 


220 


CARBON. 


SECTION  II.  CARBURETTED  HYDROGEN. 

816 

Q.  What  is  marsh-gas  or  fire-damp  ? 

A,  Carburetted  hydrogen  gas  accumulated 
on  marshes,  in  stagnant  waters,  and  coal* 
pits;  it  is  frequently  called  ^^inflammable 
air." 

817. 

Q.  What  is  carburetted  hydrogen  gas  ? 
A.  Carbon  combined  with  hydrogen 

818. 

Q.  How  in%y  carburetted  hydrogen  gas  be 
procured  on  niarshes  ? 

A.  By  stirring  the  mud  at  the  bottom  of 
any  stagnant  pool,  and  collecting  the  gas  (as 
it  escapes  upwards)  in  an  inverted  glass 
V  vessel. 

819. 

Q.  What  is  coal  gas  ? 
A.  Carburetted  hydrogen  extracted  from 
coals  by  the  I  eat  of  fire. 

820. 

Q.  Why  is  carburetted  hydrogen  gas 
called  fire-damp  or  inflammable  air  ? 

A.  Because  it  very  readily  catches  fire  ana 
exjjlodes,  when  a  light  is  introduced  to  it. 

Provided  atmosphere  air  be  present 


CARBURETTED  HYDROGEN. 


221 


821. 

Q.  Why  is  carburetted  hydrogen  gas  fre- 
:pently  called  marsh-gas  ? 

A.  Because  it  is  generated  in  meadows  and 
marshes  from  putrefying  vegetable  sub- 
stances 

See  Ignis  faluus. 
822. 

Q.  What  gas  is  evolved  by  the  wick  of 
a  burning  candle  ? 

A.  Carhuretted  hydrogen  gas :  The  carbon 
and  hydrogen  of  the  tallow  combine  into  a  gas 
from  the  heat  of  the  flame  ;  and  this  gas  is 
called  carburetted  hydrogen  or  inflammable 
air. 

823. 

Q.  Why  do  coal-mines  so  frequently  ex- 
plode ? 

A.  Because  the  carburetted  hydrogen  ga.s 
(which  is  generated  in  these  mines  by  the 
coals)  explodes,  when  a  light  is  incautiously 
introduced. 

824. 

Q.  How  can  miners  see  in  the  coal-pits  if 
tliey  may  never  introduce  a  light  ? 

A.  Sir  Humphrey  Davy  invented  a  lan- 
tern for  the  use  of  miners,  called  "the  Safety 
Lamp/'  which  may  be  used  without  danger. 
19* 


222 


CARBON. 


825. 

Q.  Who  was  Sir  Humphreij  Davy? 
A.  A  very  ingenious  chemist,  born  in 
Cornwall,  1778,  and  died  in  1829. 

826. 

Q  What  kind  of  thing  is  the  safety  lampf 
A.  A  kind  of  lantern,  covered  with  a  fine 
gauze  wire,  instead  of  glass  or  horn. 

827. 

Q.  How  does  this  fine  gauze  wire  prevent 
an  explosion  in  the  coal-mine  ? 

A.  By  preventing  the  flame  of  the  lamp 
from  communicating  with  the  inflammable 
gas  of  the  mine. 

N.  B.  The  interstices  of  the  gauze  wire  must  not  exceed  the  seventh  of 
an  inch  in  diameter 

828. 

Q.  Why  will  not  flame  pass  through  very 
fine  wire  gauze  ? 

A.  Because  the  metal  wire  is  a  very  ra- 
pid conductor  of  heat ;  and  when  the  flame 
(of  gas  burning  in  the  lamp)  reaches  the 
wire  gauze,  so  much  heat  is  conducted  away 
by  the  wire,  that  the  flame  is  extinguished. 

829. 

Q.  Does  the  gas  of  the  coal-pit  get  through 
the  wire  gauze  Into  the  lantern  ? 

A.  Yes;  and  the  inflammable  gas  ignites, 
and  burns  inside  the  lamp  :  As  soon  as  this 


PHOSPHORUS. 


223 


is  the  case,  the  miner  is  in  danger,  and  should 
withdraw. 

830. 

Q.  Why  is  the  miner  in  danger  if  the  gas 
ignites  and  burns  in  the  inside  of  the  safety 
lamp  ? 

A.  Because  the  heat  of  the  burning  gas 
will  soon  destroy  the  wire  gauze  ;  and  then 
the  flame  (being  free)  will  set  fire  to  the 
mine. 

N.  B.  When  the  carburetted  hydrogen  gas  takes  fire  from  the  miner'n 
candle,  the  miner  sometimes  perishes  in  the  blast  of  tJie  Jlame,  and  some- 
times suffers  suffocation  from  the  carbonic  acid  which  is  thus  produced. 


CHAP,  v.— PHOSPHORUS  AND  PHOSPHU- 
RETTED  HYDROGEN. 

SECTION  I.  PIIOSPHORirS. 

831. 

Q.  What  is  phosphorus  ? 

A.  A  pale  amber-colored  substance,  re- 
sembling wax  in  appearance.  The  word  is 
derived  from  two  Greek  words  which  mean 
^'to  produce  or  carry  light, cpog  cpsQeiv  [phoH- 
pherein.] 

832 

Q.  How  is  phosphorus  obtained  ? 
A.  By  heating  bones  to  a  white  heat; 
by  which  means,  the  animal  matter  and 


224       PIIOSPIIURETTED  HYDKOGEN,  ETC. 

charcoal  are  consumed  and  a  substance  called 
''phosphate  of  lime,''  is  left  behind. 

833. 

Q.  What  is  the  phosphate  of  lime? 

A.  Phosphorus  united  to  oxygen  and 
Ume  ;  when  sulphuric  acid  is  added,  and  the 
mixture  heated,  the  lime  is  attracted  to  the 
acid,  and  pure  phosphorus  remains. 

If  powdered  charcoal  be  added,  phosphorus  may  he  procured  by  dis- 
834. 

Q.  When,  and  by  whom  was  phosphorus 
discovered  ? 

A.  This  element  was  discovered  in  1669, 
l3y  Brandt  of  Hamburg. 

835. 

Q.  Is  phosphorus  inflammable  ? 

A.  It  is  so  exceedingly  inflammable  it 
sometimes  takes  fire  by  the  heat  of  the  hand; 
it  therefore  requires  great  care  in  its  ma- 
nagement as  a  blow  or  hard  rub  will  very 
often  kindle  it. 

836. 

Q.  Of  what  is  the  ignitable  part  of  Lu- 
cifer matches  made  ? 

A.  Of  phosphorus;  above  two  hundred 
and  fifty  thousand  pounds  are  used  every 
year  in  London  alone,  merely  for  the  muini- 
fncture  of  Lucifer  matches. 


PHOSPHORUS. 


228 


837. 

Q.  Why  will  Lucifer  matches  ignite  by 
merely  drawing  them  across  any  rough 
fiurface  ? 

A.  Because  they  are  made  of  phosphorus  ^ 
which  has  an  affinity  to  oxygen  at  the  low- 
est temperature ;  insomuch  that,  the  little 
additional  heat,  caused  by  the  friction  of 
the  match  across  the  bottom  of  the  lucifer- 
box,  is  sufficient  to  ignite  it;  and  at  the 
same  time  to  ignite  the  sulphur  with  which 
the  match  is  tipped. 

838. 

Q.  What  peculiar  property  has  phospho- 
rus ? 

A  It  is  luminom  in  the  dark ;  and  even 
in  day-light  appears  to  be  surrounded  by 
a  ligtit  cloud. 

839. 

Q.  Why  are  putrefying  fish  luminous  ? 

A.  Because  the  carbon  of  the  fish,  unit- 
ing with  oxygen,  forms  carbonic  acid ;  and 
the  phosphoric  acid  of  the  fish  (being  thus 
deprived  of  oxygen)  is  converted  into  phos- 
phorus :  as  soon  as  this  is  the  case,  the 
phosphorus  begins  to  unite  with  the  oxygen 
of  the  air,  and  becomes  luminous. 

Carbonic  acid  is  a  compound  of  carbon  and  oxygen. 

Phoephorfc  acid  is  a  ?ompound  of  phosphorus  and  oxygen.   If  y<m  taif 


226       PHOSPIIURETTED  ^lYDROGEN,  ETC. 

Ihe  0x5  gen  uway  from  phosphoric  acid,  the  residue,  of  course,  is  phospLu 
rus. 

The  luminousness  epoken  of,  is  due  to  the  slow  combustion  of  the  pho« 
phorus,  while  it  is  uniting  wilh  the  oxygen  of  the  air. 

840 

Q,  Why  is  the  sea  often  luminous  in  sum- 
mer time  ? 

A.  Because  the  small  jelly  fish  decay  % 
the  phosphoric  acid  which  they  contain 
(being  deprived  of  oxygen)  is  converted 
into  phosphorus,  unites  with  the  oxygen  of 
the  air,  and  becomes  luminous. 

SECTION  II.  PHOSPHURETTED  HYDROGEN. 

841. 

Q.  From  what  do  the  very  offensive  efflu- 
via of  church-yards  arise  ? 

A.  From  a  gas  called  phosphuretted  hydro- 
gen, which  is  phosphorus  combined  with 
hydrogen  gas. 

842. 

Q.  Why  does  a  putrefying  dead  body 
smell  so  offensively  ? 

A.  Because  phosphuretted  hydrogen  gas^ 
always  rises  from  putrefying  animal  sub- 
stances. 

The  escape  of  ammonia  and  sulphuretted  hydrogen  contributes  also  to 
this  offensive  smell. 

843. 

Q.  What  is  the  cause  of  the  ignis  fatuus^ 
Jack-o'Lantern,  or  Will-o'-the-wisp? 


PHOSPHORUS.  22  < 

A.  This  luminous  appearance  (which 
haunt»^  meadows,  bogs,  and  marshes,)  arises 
from  the  gas  of  putrefying  animal  and  vege- 
table substances;  especially  from  decaying 
fish. 

844. 

Q.  What  gases  arise  from  these  putrefy- 
ing substances  ? 

A.  Phospkuretted  hydrogen,  from  putrefy- 
ing animal  substances ;  and 

Carburetted  hydrogen,  from  decaying  vege'^ 
table  matters. 

845. 

Q.  How  is  the  gas  of  ignis-fatuus  ignited 
on  bogs  and  meadows  ? 

A.  Impure  phosphuretted  hydrogen 
bursts  spontaneously  into  flame,  whenever 
it  mixes  with  air  or  pure  oxygen  gas. 

Pure  phosphuretted  hydrogen  will  not  ignite  spontaneously — thrs  spon- 
tmieous  ignition  is  due  to  the  presence  of  a  small  quantity  of  ihe  vapor 
of  an  exceedingly  volatile  liquid-compound  of  phosphorus  with  hydrogen, 
which  is  occasionally  produced  wiih  the  gas  itself. 

If  phosphorus  be  boiled  with  milk  of  lime,  and  the  beak  of  the  retort 
be  placed  under  water,  bubbles  of  phosphuretted  hydrogen  will  rise  suc- 
cessively through  the  water,  and  (on  reaching  the  surface)  burst  into 

846. 

Q.  Why  does  an  ignis-fatuus,  or  Will- 
o'-the-wisp,  fly  from  us  when  we  i^un  to 
meet  it. 

A.  Because  we  produce  a  current  oi  air 
in  front  of  ourselves,  (when  we  run  toward 


228 


COMBUSTION. 


the  ignis-fatuus)  which  drives  the  light  gas 
forward, 

847. 

Q.  Why  does  an  ignis-fatuus  mn  after 
m  when  we  flee  from  it  ? 

A.  Because  we  produce  a  current  of  air 
in  the  way  we  run,  which  attracts  the  hght 
gas  in  the  same  course  ;  drawing  it  after  us 
as  we  run  away  from  it. 

848. 

Q.  May  not  many  ghost  stories  have 
arisen  from  some  ignis-fatuus,  lurking  about 
church-yards  ? 

A.  Perhaps  all  the  ghost  stories  (which 
deserve  any  credit  at  all,)  have  arisen  from 
the  ignited  gas  of  church-yards,  lurking 
about  tombs ;  to  which  fear  has  added  its 
own  creations. 


CHAP.  VL— COMBUSTION. 
849. 

Q.  How  is  heat  evolved  by  combustion  ? 

A.  By  chemical  action.  As  latent  heat  is 
liberated,  when  water  is  poured  upon  lime, 
by  chemical  action,  so  latent  heat  is  liber- 
ated in  combustion,  by  chemical  action  also- 


COMBUSTION. 


229 


850. 

Q.  What  chemical  action  takes  place  in 
combustion  ? 

A..  The  elements  of  the  fuel  combine  with 
(he  oxygen  of  the  air. 

851. 

Q.  What  three  elements  are  necessary  to 
produce  combustion  ? 

A  Hydrogen  gas,  carbon,  and  oxygen 
gas  ;  The  two  former  in  the  fuel ;  and  the 
last  in  the  air  which  surrounds  the  fuel. 

852. 

Q.  What  are  the  elements  of  fuel? 

A.  As  bread  is  a  compound  of  flour,  yeast 
and  salt ;  so  fuel  is  a  compound  of  hydro- 
gen and  carbon. 

853. 

Q.  What  causes  the  combustion  of  the 
fuel  ? 

A.  The  hydrogen  gas  of  the  fuel  (being 
set  free,  and  excited  by  a  match)  unites  with 
the  oxygen  of  the  air,  and  makes  a  yellow 
flame ;  this  flame  heats  the  carbon  of  the 
fuel,  which  (also  uniting  with  the  oxygen 
of  the  air)  produces  carbonic  acid  gas. 

854. 

Q.  What  is  fire  ? 

A.  Heat  and  light,  produced  by  the  com' 
bustion  of  inflammable  substances. 
20 


230 


COMBUSTION. 


855. 

Q  Why  does  fire  produce  heat? 
A  Because  it  liberates  latent  heat  from 
the  air  and  fuel. 

856. 

Q,  What  chemical  changes  in  air  and  fuel 
are  produced  by  combustion  ? 

A.  1st. — Some  of  the  oxygen  of  the  air 
combining  with  the  hydrogen  of  the  fueL 
condenses  into  water  ;  and 

2nd. — Some  of  the  oxygen  of  the  air, 
combining  with  the  carbon  of  the  fuel,  forms 
carbonic  acid  gas. 

857. 

Q.  Why  is  a  fire,  after  it  has  been  long 
burning,  red  hot  ? 

A.  Because  the  whole  surface  of  the  fuel 
is  so  thoroughly  heated,  that  every  part  of 
it  is  undergoing  a  rapid  union  with  the  oxy- 
gen  of  the  air. 

858. 

Q.  In  a  blazing  fire,  why  is  the  upper  sur- 
face of  the  coal  black,  and  the  lower  surface 
red? 

A.  Because  carbon  (being  solid)  requires 
a  great  degree  of  heat  to  make  it  unite  with 
the  oxygen  of  the  air.  In  consequence  of 
which,  the  hot  under  surface  of  coal  is  fre- 


COMBUSTION. 


qaeutly  redy  from  its  union  with  oxygen, 
while  the  cold  upper  surface  remains  black. 

859. 

Q.  Which  burns  the  more  quickl}^,  a 
hUizhig  fire  or  a  red  hot  one  ? 

A.  Fuel  burns  quickest  in  a  blazing  fire. 

860. 

Q.  Why  does  blazing"^  coal  burn  more 
quickly  than  red  hot  coal  ? 

A.  Because  the  inflammable  gases  of  the 
fuel  (which  are  then  escaping)  greatly  as- 
sists the  process  of  combustion. 

861. 

Q.  Why  do  the  coals  of  a  clear  bright  fire 
burn  out  more  slowly  than  blazing  coals  ? 

A.  Because  most  of  the  inflammable  gases 
and  much  of  the  solid  fuel  have  been  con- 
sumed already,  so  that  there  is  less  food  for 
combustion. 

862. 

Q.  What  is  smoke  ? 

A.  Unconsumed  parts  of  fuel  (principally 
carbon)  separated  from  the  solid  mass,  and 
carried  up  the  chimney  by  currents  of  hot 
air. 

863. 

Q.  Why  is  there  more  smoke  when  fresh 
fuel  is  added  than  when  the  fuel  is  red  hof 


*=  Bituminous  coal  Ls  the  kind  here  alluded  to. 


232 


COMBUSTION. 


A.  Because  carbon  (being  solid)  requires 
a  great  degree  of  lieat  to  make  it  unite  with 
oxygen,  (or,  in  other  words,  to  bring  it  into 
a  state  of  perfect  combustion)  when  fuel  is 
fresh  laid  on,  more  carbon  is  separated  than 
can  be  reduced  to  combustion^  and  the  surplus 
flies  off  in  smoke. 

864. 

Q.  Why  is  there  so  little  smoke  with  a  red 
hot  fire  ? 

A.  Because  the  entire  surface  of  the  fuel 
is  in  a  state  of  combustion  ;  and,  as  very  little 
carbon  remains  unconsumed,  there  is  but 
little  smoke. 

865. 

Q.  Wliy  are  there  bright  and  dark  spots  in 
a  clear  cinder  fire  ? 

A.  Because  the  intensity  of  the  combus« 
tion  is  greater  in  some  parts  of  the  fire  than 
it  is  in  others. 

866. 

Q.  Why  is  the  intensity  of  the  combus- 
tion so  unequal  ? 

A,  Because  the  air  flies  to  the  fire  in 
various  and  unequal  currents. 

867. 

Q.  Why  do  we  see  all  sorts  of  grotesqw 
figures  in  hot  coals  ? 


COMBUSTION 


233 


A.  Because  the  intensity  of  combustion  is 
unequal  (owing  to  the  gusty  manner  in  which 
the  air  flies  to  the  fuel ;)  and  the  various 
shades  of  yellow,  red,  and  white  heat 
(mingling  with  the  black  of  the  unburnt 
ijoal,)  produce  strange  and  fanciful  resem- 
blances. 

868. 

Q.  Why  does  paper  hum  more  readily 
than  wood  ? 

A.  Because  it  is  of  a  more  fragile  texture ; 
and,  therefore,  its  component  parts  are  more 
easily  heated. 

869. 

Q.  Why  does  wood  hum  more  leadily  than 
coal  ? 

A.  Because  it  is  not  so  solid;  and,  there- 
fore, its  elemental  parts  are  more  easily 
separated  and  made  hot. 

870. 

Q.  When  a  coal  fire  is  lighted,  why  is  pa- 
per laid  at  the  hottom  against  the  grate  ? 

A.  Because  paper  (in  consequence  of  its 
fragile  texture)  very  readily  catches  fire. 

871. 

Q.  Why  is  wood  laid  on  the  top  of  the 
paper  ? 

A.  Because  wood  (being  more  snbstonfi a!) 
20* 


234 


COMBUSTION. 


burns  longer  than  paper;  and,  therefore 
affords  a  longer  contact  of  flame  to  heat  the 
coal . 

872. 

Q.  Why  would  not  paper  do  without  wood? 

A.  Because  paper  burns  out  so  rapidly^ 
that  it  would  not  afford  sufficient  contact  of 
flame  to  heat  the  coal  to  combustion. 

873. 

Q.  Why  will  not  wood  kindle  without 
shavings,  straw,  or  paper  ? 

A.  Because  wood  is  too  substantial  to  be 
heated  into  combustion  by  the  feeble  flame 
issuing  from  a  match. 

874. 

Q.  Why  would  not  paper  do  as  well  if 
placed  on  the  top  of  the  wood  ? 

A.  Because  the  blaze  tends  upwards ;  if 
therefore,  the  paper  were  placed  on  the  top, 
its  blaze  would  afford  no  contact  of  flame  to 
the  fuel  lying  helow. 

875. 

Q.  Why  should  coal  be  placed  above  tho 
wood  ? 

A.  Because  otherwise,  the  flame  of  the 
fuel  would  not  rise  through  the  coal  to  heat  it. 

876. 

Q.  Why  is  a  fire  kindled  at  the  lowest  bar 
of  the  grate  ? 


COMBUSTION. 


235 


A,  That  the  flame  may  ascend  through 
the  fuel  to  heat  it.  If  the  fire  were  kindled 
from  the  top,  the  flame  would  not  come  in 
contact  with  the  fuel  placed  below. 

877. 

Q.  Why  will  cinders  become  red  hot  more 
quickly  than  coal  ^ 

A.  Because  they  are  sooner  reduced  to  a 
state  of  combustion,  as  they  are  more  porous 
and  less  solid. 

878. 

Q.  Why  are  cinders  lighter  than  coal  ? 

A.  Because  they  are  full  of  little  holes ; 
from  which  vapor,  gases,  and  other  volatile 
parts,  have  been  driven  off  by  previous 
combustion. 

879. 

Q.  Why  will  not  wet  kindling  light  a  fire? 

A.  1st. — Because  the  moisture  of  the  wet 
kindling  prevents  the  oxygen  of  the  air  from 
getting  to  the  fuel ;  and 

2nd.- — The  heat  of  the  fire  is  perpetually 
drawn  off  by  the  conversion  of  water  into 
steam. 

880. 

Q.  Why  does  dry  wood  bum  better  than 
%reen  ? 

A.  1st. — Beonn.se  none  of  its  heat  is  car- 


236 


COMBUSTION. 


ried  aioay  by  the  conversion  <^f  water  into 
steam  ;  and 

2nd. — The  pores  of  dry  wood  (being  fill- 
ed with  air)  supply  the  fire  with  oxygen. 

881. 

Q.  Why  do  two  pieces  of  wood  burn  bet- 
iei  than  one  ? 

A.  1st. — Because  they  help  to  entangle 
the  heat  of  the  passing  smoke,  and  throw  it  on 
the  fuel ;  and 

2nd.— The  air,  impinging  against  the 
pieces  of  wood,  is  thrown  upon  the  fire  m  a 
kind  of  eddy  or  draught. 

882. 

Q.  Why  will  not  wood  or  paper  hum  if 
steeped  in  a  solution  of  potash ,  phosphate  of 
lime,  or  ammonia  (hartshorn?) 

A.  Because  any  "  alkali "  (such  as  potash) 
will  arrest  the  hydrogen  which  escapes  from 
the  fuel,  and  prevent  its  combination  with  the 
oxygen  of  air. 

883. 

Q.  Why  does  a  jet  of  flame  sometimes 
burst  into  the  room  through  the  bars  of  a 
stave  ? 

A.  Because  the  iron  bars  conduct  heat  to 
the  interipr  of  the  coal,  and  its  volatile  gas 
fbur:^^iAif  through  the  weakest   part)  is 


COMBUSTION. 


237 


kindled  by  the  glowing  coals  over  which  it 
passes. 

834. 

Q.  Why  is  this  jet  sometimes  of  a  greenish 
yellow  color  ? 

A.  Either  because  some  lumps  of  coal  lie 
over  the  hot  bars  ;  or  else  the  coal  below  is 
not  red  hot ;  in  consequence  of  which,  some 
of  the  gas  escapes  unhurnt^  and  is  of  a  green- 
ish color. 

885. 

Q.  Why  does  the  gas  escape  unhurnt  ? 
A.  Because  neither  the  hars  nor  the  coal 
over  which  it  passes  are  red  hot. 

886. 

Q.  ^yiiy  does  a  bluish  flame  sometimes 
flicker  on  the  surface  of  hot  cinders  ? 

A.  Because  the  gas  from  the  hot  coal  at 
the  bottom  of  the  grate,  mixing  with  the  car- 
bon of  the  coal  above,  produces  an  inflamma- 
ble gas  (called  carbonic  oxide)  which  burns 
with  a  blue  flame. 

887. 

Q.  Why  is  the  light  of  a  fire  more  intense 
Bometimes  than  it  is  at  others  ? 

A.  The  intensity  of  fire-light  depends 
upon  the  whiteness  to  w^hich  the  carbon  is 
reduced  by  combustion.   If  carbon  be  rvhite- 


238 


COMBUSTION. 


hot  its  combustion  is  perfect ,  and  thi  light  in 
tense ;   if  not  the  hght  is  obscured  bv 
moke. 

883. 

Q.  Why  will  not  cinders  blaze  as  well  as 
fresh  coal? 

A.  The  flame  of  coal  is  made  chiefly 
by  hydrogen  gas.  As  soon  as  this  gas  has 
been  consumed,  the  hot  cinders  produce 
only  a  gas,  called  carbonic  acid,  which  is 
neither  luminous  nor  visible 

889. 

Q.  Where  does  the  hydrogen  gas  of  a  fire 
come  from  ? 

A.  All  fuel  is  composed  of  csiYhon  and  hy- 
drogen gas,  which  are  separated  from  eacL 
other  by  the  process  of  combustion. 

890. 

Q.  Why  does  not  afire  blaze  on  a  f?osty 
night,  so  long  as  it  does  upon  another 
night  ? 

A.  1st. — Because  air  condensed  by  the 
cold  contains  more  oxygen  than  tbe  same 
quantity  of  warmer  air ;  and 

2nd. — Air  condensed  by  the  cold  is  hea* 
vier  ;  in  consequence  of  which,  it  falls  more 
quickly  on  the  fire  to  supply  the  j)lace  of 
the  hot  ascending  air. 


COMBUSTION. 


239 


891. 

Q.  WTiy  does  a  fire  bum  clearest  on  a 
frosty  night. 

A.  Because  the  volatile  gases  are  more 
quickly  consumed ;  and  the  solid  carbon  is 
plentifully  supplied  with  oxygen  from  the  air 
to  make  it  burn  brightly  and  intensely. 

892. 

Q.  Why  does  a  fire  burn  more  intensely 
in  winter  than  in  summer  ? 

A.  Because  the  air  is  colder  in  winter 
than  it  is  in  summer. 

893. 

Q.  Why  does  the  coldness  of  the  air  in- 
crease  the  heat  of  a  fire. 

A.  1st. — Because  air  condensed  by  the 
cold  supplies  more  oxygen  than  a  similar 
volume  of  warmer  air ;  and 

2nd. — Condensed  air  being  heavy,  falls 
more  rapidly  into  the  place  of  the  hot  as- 
cending air,  to  supply  the  fire  with  nourish- 
ment. 

894. 

Q.  Ashes  or  cinders  are  put  over  the  fire 
at  night  to  prevent  its  burning  away.  Can 
you  tell  the  reason  for  thus  covering  the 
fire  ? 

A.  Tlie  ashes  or  cinders  prevent  the  oxy* 


240 


COMBUSTION. 


gen  of  the  air  from  gaining  free  access  to 
the  fire  ;  and  as  fire  will  not  burn  without 
a  supply  of  oxygen  it  keeps  alive  for  seve- 
ral hours  without  being  wasted. 

895. 

Q.  Why  does  the  sun  shining  on  si  fir. 
make  it  dull  and  often  put  it  out  ? 

A.  1st. — Because  the  air  (being  rarefied 
by  the  sunshine)  flows  more  slowly  to  the 
fire  ;  and 

2nd. — Even  that  which  reaches  the  fire 
affords  less  nourishment. 

Sunshine  produces  also  some  chemical  effect  upon  the  air  or  fuel  detri- 
mental to  combustion. 

f96. 

Q.   Why  does  the  air  flow  to  the  fire 

more  tardily  for  being  rarefied  ? 

A.  Because  the  greater  the  contrast  be- 
tween the  external  air,  and  that  which  has 
been  heated  by  the  fire,  the  more  rapid  will 
be  the  current  of  air  toward  that  fire. 

897 

Q.  Why  does  rarefied  air  afford  less 
nourishment  to  fire  than  cold  air  ? 

A.  Because  rarefied  air  contains  less  oxy- 
gen, than  the  same  quantity  of  condensed 
air. 

Inasmuch  as  the  same  quantity  of  oxygen  is  diffused  over  a  larger  vo- 
^iKie  of  air. 


COMBUSTION.  241 
898. 

Q.  Why  does  a  fire  burn  more  fiercely  in 
the  open  air  ? 

A.  1st. — Because  the  air  out  of  doors  ib 
iT^ore  deiiu,  than  the  air  in  doors ;  and 

2nd. — It  has  freer  access  to  the  fire. 

899. 

Q.  'Why  is  the  air  out  of  doors  more 
deiise  than  that  in  doors  ? 

A.  Because  it  has  freer  circulation  ;  and, 
as  soon  as  any  portion  has  been  rarefied,  it 
instantly  escapes,  and  is  supplied  by  colder 
currents. 

900. 

Q.  Why  does  not  a  J^re  burn  so  fiercely  in 
a.  thaw  as  in  a  frost  ? 

A.  Because  the  air  is  laden  with  vapor, 
in  consequence  of  which,  it  both  moves  too 
slowly,  and  is  too  much  rarefied,  to  nourish 
the  fire. 

901. 

Q.  Why  does  a  fire  burn  so  fiercely  in 
windy  weather  ? 

A.  Because  the  air  is  rapidly  changed,  and 
affords  plentiful  nourishment  to  the  fire. 

902. 

Q.  Why  does  a  pair  of  bellows  get  a  fire 
up? 

21 


242 


COMBUSTION. 


A.  Because  it  drives  the  air  more  rapidly 
to  the  fire;  and  the  plentiful  supply  of 
oxygen  soon  makes  the  fire  burn  intensely 

903. 

Q.  What  gas  is  generated  in  a  commoD 
fire  by  combustion  ? 

A.  Carbonic  acid  gas,  formed  by  the  union 
of  the  carbon  of  the  fuel  with  the  oxygen 
of  the  air. 

S04. 

Q.  What  is  carbonic  acid  gas  ? 
A,  Only  carbon  (or  charcoal)  combined 
with  oxygen  gas. 

905. 

Q.  If  a  piece  of  paper  be  laid  flat  on  a 
clear  fire,  it  will  not  blaze,  but  char.  Why 
so? 

A.  Because  the  carbon  of  a  clear  fire,  be- 
ing sufiiciently  hot  to  unite  with  the  oxy- 
gen of  the  air,  produces  carbonic  acid  gas, 
which  soon  envelopes  the  paper  laid  flat 
apon  the  cinders;  but  carbonic  acid  gas 
aot  blaze. 

906 

Q.  If  you  blow  the  paper,  it  will  blaze 
immediately.    Why  so  ? 

A.  Because  by  blowing  or  opening  a  door 
suddenly,  the  carbonic  acid  is  dissipated,  and 
the  paper  fanned  into  flame. 


COMBUSTION. 


243 


907. 

Q.  Wh}  does  water*  extinguish  a  Jire  ? 

A.  1st. — Because  the  watei  formsacoat^ 
tag  over  the  fuel,  which  keeps  it  from  the 
air;  and 

2nd. — The  conversion  of  water  into  steamy 
draws  off  the  heat  of  the  burning  fuel. 

908. 

Q.  A  little  water  makes  a  fire  fiercer,  while 
a  larger  quantity  of  water  puts  it  out.  Ex- 
plain how  this  is  ? 

A.  Water  is  composed  of  oxygen  and  hy- 
drogen; when,  therefore,  the  fire  can  decom- 
pose the  water  into  its  simple  elements,  it 
serves  for  fuel  to  the  flame. 

909 

Q.  How  can  water  serve  for  fuel  to  fire 
A.  Because  the  hydrogen  of  the  water 
burns  with  a  flame  ;  and  the  oxygen  of  the 
water  increases  the  intensity  of  that  flame 

910. 

Q.  liVhen  a  house  is  on  fire,  is  too  littk 
water  worse  than  none? 

A.  Certainly.  Unless  water  be  supplied 
BO  plentifully  as  to  quench  the  fire,  it  will  in* 
crease  its  intensity,  like  fuel. 

911. 

Q,  Why  will  water  extinguish  fire  ? 


COMBUSTION. 


A.  Wlien  the  supply  is  so  rapid  ana 
abundant,  that  the  fire  cannot  decompose  it. 

912. 

Q.  Does  not  a  very  little  watei  slacken  the 
heat  of  fire  ? 

A.  Yes,  till  it  (the  water)  is  decomposed; 
it  then  increases  the  intensity  of  fire,  and 
acts  like  fuel. 

913. 

Q.  Cannot  wood  be  made  to  hlaze  with- 
out actual  contact  with  fire  ? 

A.  Yes ;  if  a  piece  of  wood  be  held  near 
the  fire  for  a  little  time,  it  will  blaze,  even 
though  it  does  not  touch  the  fire. 

914. 

Q.  Why  will  wood  hlaze,  even  if  it  does 
not  touch  the  fire  ? 

A.  Because  the  heat  of  the  fire  drives  out 
the  hydrogen  gas  of  the  wood;  which  gas  is 
inflamed  by  contact  with  the  red  hot  coals. 

915. 

Q.  Why  will  a  neighbor^ s  house  sometimes 
catch  fire,  though  no  flame  of  the  burning 
house  ever  touches  it  ? 

A.  Because  the  heat  of  the  burning  house 
Bets  a.t  liberty  the  hydrogen  gas  of  the  wood- 
work of  the  neighbor's  house  ;  and  tliis  gas 


COMBUSTION.  245 

is  ignited  by  the  flames  or  red  hot  I  ricks  of 
the  house  on  fire. 

916. 

Q.  On  what  does  the  intensity  of  fire  de- 
pend ? 

A.  The  vitensity  of  fire  is  always  in  pro- 
^X)rtion  to  the  quantity  of  oxygen  with  which 
it  is  su]3plied. 

917. 

Q.  Why  is  a  dull  fire  revived  by  sweeping 
clean  the  hearth,  bars  of  the  grate,  and- 
irons, etc. 

A.  Because  the  air,  which  was  arrested 
by  the  loose  dust  and  cinders,  finds  its  way 
freely  to  the  fire,  as  soon  as  these  obstacles 
are  swept  away. 

The  brightness  of  a  fire  depends  on  its  supply  of  oxygen  derived  from 
Ihe  air, 

918. 

Q.  Why  does  stirring  a  dull  fire  serve  to 
quicken  it  ? 

A.  Because  it  breaks  up  the  clotted  cin- 
ders and  coals,  making  a  passage  for  the  aU 
into  the  very  heart  of  the  fire. 

A  cofil  fire  should  be  stirred  fror.  che  bottom  and  not  from  the  top. 
919. 

Q.  Why  will  powdered  sulphur  quench  fire 
more  readily  than  water  ? 

A.  1st. — Because  powdered  sulphur  has 
21* 


246 


COMBUSTION. 


a  very  strong  affinity  for  oxygen,  and  con 
verts  it  into  sulphurous  acid ;  as  this  is  th<i 
case,  the  fire  is  deprived  of  its  essential  food, 
(oxygen)  and  is,  in  fact,  starved  out ;  and 

2nd. — Because  sulphurous  acid  throws  off 
dense  white  fumes,  and  surrounds  the  fire 
with  an  extinguishing  atmosphere. 

The  difference  between  pulpburous  acid  and  sulphuric  acid,  is  this  :  sul- 
phurous acid  contains  less  oxygen  than  sulphuric  acid.  When  we  burn 
sulphur  in  air,  it  throws  off  suffocating  white  fumes,  called  sulphurout 
acid. 

920. 

Q.  Why  do  lamps  smoke  ? 

A.  Either  because  the  wick  is  cut  un- 
evenly^ or  else,  because  it  is  raised  up  too 
high. 

921. 

Q.  Why  does  a  lamp  smoke  when  the  wick 
is  cut  unevenly  ? 

A.  1st. — Because  the  points  of  the  jagged 
edge  (being  very  easily  separated  from  the 
wick)  load  the  flame  with  more  carbon  than  it 
can  consume  ;  and 

2nd. — As  the  heat  of  the  flame  is  greatly 
diminished  by  these  bits  of  wick,  it  is  unable 
to  consume  even  the  usual  quantity  of  smoke. 

922. 

Q.  Why  does  a  lamp  smoke  when  tlic  wick 
is  turned  up  too  high  ? 


COMBUSTION. 


247 


A .  Because  more  carbon  is  separated  from 
the  wick  ^han  can  he  consumed  hy  the  flame, 

923. 

Q.  Why  do  not  Argand  hurntrs  smoke  ? 

A.  Because  a  current  of  air  passes 
through  the  middle  of  the  flame  ;  in  conse- 
quence of  which,  the  carbon  of  the  interior 
is  consumed,  as  well  as  that  in  the  outer  coat^ 
ing  of  the  flame. 

924. 

Q.  Why  does  a  lamp  glass  diminish  the 
smoke  of  a  lamp  ? 

A.  1st. — Because  it  increases  *the  sup- 
ply of  oxygen  to  the  flame,  by  producing  a 
draught;  and 

2nd. — It  concentrates  and  reflects  the  heat 
of  the  flame  ;  in  consequence  of  which,  the 
combustion  of  the  carbon  is  more  perfect^ 
and  very  little  escapes  unconsumed. 

925. 

Q.  What  causes  the  heat  of  fire  ? 

A.  The  carbon  of  fuel  (when  heated)  com- 
bines with  the  oxygen  of  the  air,  and  pro- 
duces carbonic  acid  gas :  Again,  the  hydrogen 
of  the  fuel  combining  with  other  portions  of 
oxygen,  condenses  into  ivater ;  by  which 
riiemical  actions  heat  is  evolved. 


248 


COMBUSTION. 


926. 

Q.  Whence  does  the  heat  of  a  dunghill 
arise  ? 

A.  As  the  straw,  etc.,  of  the  dunghill  de- 
cays, it  undergoes  fermentation,  which  pro- 
'Juces  carbonic  acid  gas  ;  and  heat  is  evolved 
hy  a  species  of  combustion. 

SECTION  I.  SPONTANEOUS  COMBUSTION. 

927. 

Q.  What  is  meant  by  spontaneous  comhus- 
Hon? 

A.  Combustion  produced  without  the  ap- 
plication of  flarne. 

928. 

Q.  Give  me  an  example  of  spontaneous 
combustion  ? 

A.  Goods  packed  in  a  warehouse  w^ill 
often  catch  fire  of  themselves,  especially  such 
goods  as  cotton,  flax,  hemp,  rags,  etc. 

929. 

Q.  Why  do  such  goods  sometimes  catch 
fire  of  themselves? 

A.  Because  they  are  piled  together  in 
very  large  masses  in  a  damp  state  or  places, 

930. 

Q.  What  is  generally  the  cause  of  spori' 

taneous  comhmtion  ? 


SPONTANEOUS  COMBLSTION. 


249 


A.  The  piled-up  goods  ferment  fiom  heat 
und  damp,  and  (during  fermentation)  car- 
bonic acid  gas  is  formed,  which  is  attended 
with  combustion. 

S31. 

Q.  Why  does  this  jDroduce  spontaneous 
(?ombustion  ? 

A.  The  damp  produces  decay,  or  the  de- 
composition of  the  goods;  and  the  great 
heat  of  the  piled  up  mass  makes  the  decay- 
ing goods  ferment. 

932. 

Q.  How  does  this  fermentation  produce 
combustion  ? 

A.  During  fermentation  carbonic  acid  gas 
is  given  off  by  the  goods, — a  slow  combus- 
tion ensues, — till  at  length  the  ivhole  pile 
bursts  into  flame. 

933. 

Q.  Why  is  the  heat  of  a  large  mass  of 
goods  greater  than  that  of  a  smaller  quantity? 

A.  Because  the  carbonic  acid  cannot  es- 
cape through  the  massive  pile ;  and  fclio 
products  of  decomposition  being  confined^ 
hasten  further  changes 

934, 

Q.  Why  do  hay-stocks  sometimes  catch 
fire  of  themselves  ? 


250 


COMBUSTION. 


A.  Either  because  the  hay  was  put  up 
^amp  ;  or  else,  because  rain  has  penetrated 
the  stack. 

935. 

Q.  Does  heat  always  produce  light? 

A.  No ;  the  heat  of  a  stack  of  hay,  or 
rocking  dunghill,  though  very  great,  is  not 
sufficient  to  produce  light. 

936. 

Q.  Why  will  a  hay-stack  catch  fire,  if  the 
hay  be  damp  ? 

A.  Because  damp  hay  soon  decays,  and 
undergoes  a  state  of  fermentation  ;  during 
which  carbonic  acid  gas  is  given  off,  and  the 
stack  catches  fire. 

937 

Q.  Why  do  greasy  rags  sometimes  catch 
fire? 

A.  Because  they  very  readily  ferrtLtit.^ 
and  (during  fermentation)  throw  off  exceed- 
ingly inflammable  gases. 

Lamp-black,  mixed  with  linseed  oil,  is  very  liable  to  spontaneous  «cii' 
iBfltion. 

SECTION  II.  FLAME. 

938. 

Q.  What  is  fame  ? 

A.  The  rapid  combustion  of  volatile  matter 


FLAME. 


2oJ 


939. 

Q  Why  is  the  flame  of  a  good  Are  yellow  ? 

A.  Because  both  the  hydrogen  and  car- 
bon of  the  fuel  are  m  a  state  of  perfect  cont" 
bust  ion.  It  is  the  white  heat  of  the  carbon, 
which  gives  the  pale  yellow  tinge  to  the 
flaming  hydrogen. 

940. 

Q.  Why  is  a  yellow  flame  brighter  than  a 
red  hot  coal  ? 

A.  Because  yellow  rays  produce  the 
greatest  amount  of  light,  though  red  rays 
produce  the  greatest  amount  of  heat. 

941 

Q.  Why  is  the  flame  of  a  candle  extinguish- 
ed when  blown  by  the  breath ;  and  not 
made  more  intense  like  a  fire  ? 

A.  Because  the  flame  of  a  candle  is  con- 
fined to  a  very  small  loick,  from  which  it  is 
severed  by  the  breath;  and  (being  unsup- 
ported) must  go  nut. 

942. 

Q.  Why  is  a  smouldering  wick  sometimes 
rekindled  by  blowing  it  ? 

A.  Because  air  is  carried  to  it  by  the 
breath  with  great  rapidity  y  and  the  oxygen 
of  the  air  kindles  the  red  hot  loick,  as  it 
would  kindle  charred  wood. 


252 


COMBUSTION. 


943. 

Q.  Why  is  not  the  red  hot  wick  kindled 
by  the  air  around  it  without  blowing  ? 

A.  Because  oxygen  is  not  supplied  with 
sufficient  freedom,  unless  air  be  blown  to  the 
wick. 

944, 

Q.  When  is  this  experiment  most  likely 
to  succeed  ? 

A.  In  frosty  weather;  because  the  air 
contains  more  oxygen,  when  it  is  condensed 
hy  the  cold. 

S45. 

Q.  Why  does  the  wick  of  a  candle  (when 
the  flame  has  been  blown  out)  very  readily 
catch  fire  ? 

A.  Because  the  wick  is  already  hot^  and 
a  very  little  extra  heat  will  throw  it  into 
flame. 

946. 

Q.  Why  does  the  extra  heat  revive  the 
flame? 

A.  Because  it  again  liberates  the  hydro- 
gen of  the  tallow,  and  ignites  it. 

947. 

Q.  A  candle  burns  when  lighted  ;  explain 
how  this  is  ? 

A.  1st. — The  heat  of  the  lighted  wick 
decomposes  the  tallow  into  its  elementary 


FLAME. 


253 


parts  of  carbon  and  hydrogen ;  and  the  hy- 
drogen of  the  tallow,  combining  with  the 
oxygen  of  the  air,  produces  flame  ;  and 

2nd. — The  substance  in  the  wick,  having 
its  temperature  raised  by  the  application  of 
heat,  combines  with  the  oxygen  of  the  at- 
mosphere, and  this  combination  attended 
with  the  evolution  of  heat,  sustains  the  pro- 
cess of  combustion. 

948. 

Q.  Where  is  the  tallow  or  wax  of  a  can- 
dle decomposed  ? 

A.  In  the  wick.  The  melted  tallow  or 
wax,  rises  up  the  wick  by  capillary  attrac- 
tion, and  is  rapidly  decomposed  by  the  heat 
of  the  flame. 

(For  a  definition  of  capillary  attraction  see  under  the  proper  head.) 
949 

Q.  Why  is  the  flame  of  a  candle  hot  ? 
A.  Because  the  flame  liberates  latent  heat 
from  the  air  and  tallow 

950. 

Q.  How  is  latent  heat  liberated  by  the 
flame  of  a  candle  ? 

A.  When  the  elements  of  the  tallow 
combine  with  the  oxygen  of  the  air,  latent 
heat  is  liberated  by  the  chemical  (^.hanges 
22  ' 


254 


COMBUSTION. 


951. 

Q.  Why  does  the  flame  of  a  candle  pre 
duce  light  ? 

A.  Because  the  chemical  changes  made 
by  combustion,  excite  undulations  of  ether 
(which  striking  the  eye)  produce  light. 

952. 

Q.  Why  is  the  flame  of  a  candle  yellow  ? 

A.  It  is  not  entirely  so ;  only  the  outer 
coat  of  the  flame  is  yellow^  the  lower  part  is 
violet ;  and  the  inside  of  the  flame  hollow. 

953. 

Q.  Describe  the  different  parts  of  the 
flame  of  a  common  candle  ? 

A.  The  flame  consists  of  three  cones.  The 
innermost  cone  is  hollow,  the  outside  cone 
is  yellow,  and  the  intermediate  one  is  of  a 
dingy  purple  hue. 

954. 

Q.  Why  is  the  outside  of  the  flame  yeU 
low  ? 

A.  Because  the  carbon  of  the  tallow  (being 
in  a  state  of  perfect  combustion)  is  made 
white-hot. 

955. 

Q.  Why  is  the  lower  part  of  the  flame 
Tpurple? 

A  Because  it  is  overladen  tvith  hydrogen^ 


% 


FLAME. 


255 


raised  from  the  tallow  by  the  burning  wick, 
and  this  gas  (which  burns  with  a  blue  flame,) 
gives  the  dark  tinge  to  the  lower  part  of 
the  candle  flame. 

956. 

Q  Why  is  the  inside  of  the  flame  hollow? 

A  Because  it  is  filled  with  vapor,  raised 
from  the  candle  by  the  heat  of  the  wick,  and 
not  yet  reduced  to  a  state  of  combustion, 

957. 

Q.  Why  is  the  intermediate  cone  of  a 
flame  purple  as  well  as  the  bottom  of  the 
flame  ? 

A.  Because  the  gases  are  not  in  a  state 
of  perfect  combustion  ;  but  contain  an  excess 
of  hydrogen,  which  gives  the  flame  a  purple 
tinge. 

958 

Q.  Why  is  not  the  middle  cone  in  a 
state  of  perfect  combustion,  as  well  as  the 
obiter  one  ? 

A.  Because  the  outer  cone  prevents  Ike 
oxygen  of  the  air  from  getting  to  the  middle 
of  the  flame,  and  without  the  free  access 
of  oxygen  gas,  there  is  no  such  thing  as 
complete  combustion. 

959. 

Q.  Why  does  the  flame  of  a  candle  point 
upwatds? 

4 


256 


COMBUSTION. 


A.  Because  it  heats  the  surrounding  air^ 
wliicli  (being  liot)  rapidly  ascends,  driving 
the  flame  upwards  at  the  same  time. 

960 

Q.  Why  is  the  flame  of  a  candle  pointed 
at  the  top  like  a  cone  ? 

A.  Because  the  upper  part  of  a  flame  is 
more  volatile  than  the  lower;  and,  as  it 
aflbrds  less  resistance  to  the  air,  is  reduced  to 
a  mere  point. 

961. 

Q.  Why  are  the  lotver  parts  of  a  flame 
less  volatile  than  the  upper  ? 

A.  Because  they  are  laden  with  uncon- 
sumed  gas  and  water?/  vapor,  which  present 
considerable  resistance  to  the  air. 

962. 

Q.  "Why  is  the  flame  of  a  candle  blown 
out  by  a  puff*  of  breath  ? 

A.  Because  it  is  severed  from  the  wick  and 
goes  out  for  want  of  support. 

963. 

Q.  Why  does  the  flame  of  a  candle  make 
a  glass  (which  is  held  over  it)  damp  ? 

A>  Because  a  "watery  vapor''  is  made, 
by  the  combination  of  the  hydrogen  of  taU 
low  with  the  oxygen  of  the  air ;  and  this 


V 


FLAME. 


257 


*' vapor''  is  condensed  by  the  cold  glass  held 
above  the  flame. 

964. 

Q.  Why  does  the  hand,  held  above  a  can- 
dle, suffer  more  from  heat,  than  when  it  is 
placed  below  the  flame,  or  on  one  side  of  it. 

A.  Because  the  hot  gases  and  air  (in 
their  ascent)  come  in  contact  with  the  hand 
placed  above  the  flame ;  but  when  the  hand 
is  placed  belovj  the  flame,  or  on  one  side,  it 
only  feels  heat  from  radiation. 

"  Radiation," — tliat  is,  emission  of  rays.  The  candle  flame  throws  oul 
rays  of  light  and  heat  in  all  directions;  but  when  the  hand  is  held  above 
the  flame,  it  not  only  feels  the  heat  of  the  rays  but  also  of  the  ascending 
current  of  hot  air,  etc. 

965. 

Q.  Why  is  a  rush-light  extinguished  more 
readily  than  a  cotton  wick  candle  ? 

A.  Because  a  hafd  rush  imbibes  the 
melted  fat  or  wax  much  more  slowly  than 
porous  cotton ;  as  it  imbibes  less  fat,  it  sup- 
plies a  smaller  volume  of  combustible  gases^ 
and,  of  course,  the  light  is  more  easily  ex- 
tinguished. 

966. 

Q.  Why  is  it  more  difficult  to  blow  out  a 
cotton  wick  than  a  rush-light  ? 

A.  Because  porous  cotton,  imbibes  the 
melted  fat  or  wax,  much  more  readily  than 
hard  rush;  as  it  imbibes  more  fat,  it  sup- 
22^ 


258 


COMBUSTION. 


plies  the  flame  with  a  larger  volume  of 
combustible  gases  ;  and,  of  course,  the  light  is 
with  more  difficulty  extinguished. 

967. 

Q.  Why  is  a  gas  flame  more  easily  ex- 
tinguished when  the  jet  is  very  slightly 
turned  on,  than  when  it  is  in  full  stream? 

A.  Because  there  is  less  volume  of  com- 
bustible gases  in  the  small  flame,  than  in 
the  full  blaze. 

968. 

Q.  Why  does  an  extinguisher  put  a  can- 
dle out? 

A.  Because  the  air  in  the  extinguisher 
is  soon  exhausted  of  its  oxygen  by  the  flame; 
and  when  there  is  no  oxygen  flame  goes 
out. 

969. 

Q.  Why  does  not  a  candle  set  fire  to  a 
piece  of  paper  twisted  into  an  extinguisher, 
and  used  as  such? 

A.  1st. — Because  the  flame  very  soon 
exhausts  the  oxygen  contained  in  the  paper 
extinguisher;  and 

2nd. — The  flame  invests  the  inside  of  the 
paper  extinguisher  with  carbonic  acid  gaSt 
which  prevents  it  from  blazing. 


FLAME. 


259 


970. 

Q.  Why  is  a  long  wick  never  upright  ? 
A.  Because  it  is  bent  by  its  own  weight. 

971. 

Q.  A  long  wick  is  covered  with  an  ^^fflor^ 
escence  at  the  top.  What  does  this  aris^o 
fiom  ? 

A.  The  knotty  or  flowery  appearance  of 
the  top  of  a  wick  arises  from  an  accumula- 
tion of  particles  partly  separated  but  still 
loosely  hanging  to  the  wick. 

972. 

Q.  \Yliy  do  common  candles  require  snuff- 
ing? 

A.  Because  the  heat  of  the  flame  is  not 
sufficient  to  consume  the  wick;  and  the  longer 
the  wick  grows  the  less  heat  the  flame  pro- 
duces. 

973. 

Q.  Why  do  wax  candles  never  nee  J 
snuffing  ? 

A.  Because  the  wick  of  wax  candles  is 
made  of  very  fine  thread,  which  the  heat  of 
the  flame  is  sufficient  to  consume.  The 
wick  of  tallow  candles  (on  the  other  hand,) 
is  made  of  coarse  cotton,  which  is  too  sub- 
stantial to  be  consumed  by  the  heat  of  ih^ 
flame,  and  must  be  cut  off  by  snuffers. 


260 


COMBUSTION. 


974. 

Q.  Why  does  a  pin  stuck  in  a  rush-light 
p.xtinguish  it  ? 

A.  Because  n>  pin  (being  a  good  conduc- 
tor) carries  away  the  heat  of  the  flame  from 
the  wick,  and  prevents  the  combustion  of 
the  tallow. 

975. 

Q.  What  is  the  smoke  of  a  candle? 

A.  Solid  particles  of  carbon,  separated 
from  the  wick  and  tallow,  but  not  con- 
sumed. 

976. 

Q.  Why  are  some  particles  consumed  and 
not  others  ? 

A.  The  combustion  of  the  carbon  depends 
upon  its  combining  with  the  oxygen  of  the  air ; 
now  as  the  outer  surface  of  the  jflame  pre- 
vents the  access  of  air  to  the  interior  parts, 
much  of  the  carbon  of  those  parts  passes 
off  in  smoke. 

977. 

Q.  Why  does  a  candle  flicker,  especially 
just  previous  to  its  being  burnt  out  ? 

A.  Because  it  is  unequally  supplied  with 
combustible  gases.  When  a  candle  is 
nearly  burnt  out,  there  is  not  sufficient  tal- 
low or  y/ax  to  keep  up  the  regular  supply 


FLAME. 


of  combustible  gas ;   in  consequence  of 
which,  the  flame  flickers,  that  is,  blazes^ 
when  it  is  supplied  with  gas,  and  goes 
out  for  a  moment  when  the  supply  is  do 
fective. 


PART  111. 

METALS. 


CHAP.  L— METALS  AND  ALLOYS. 

SECTION  I.  METALS. 
978. 

Q.  If  you  heat  steel  red  hot\n  the  fire,  and 
then  plunge  it  suddenly  into  cold  water  it 
becomes  hard  and  hrittle  ;  why  is  this  ? 

A.  Because  the  sudden  chill  violently  ex- 
pels the  latent  heat,  which  would  have 
settled  in  the  steel,  had  it  been  allowed  to 
cool  slowly. 

The  malleability  and  toughness  of  metals  depend  -  upon  their  power  of 
; absorbing  heat. 

979. 

Q.  What  is  Uock  tin  ? 
A.  Tin  purified  by  heat,  and  run  into 
moulds,  which  ^orm  blocks  of  great  size. 

980. 

Q.  What  is  sheet  tin,  such  as  is  used  in  tlie 
manufacture  of  pans  and  other  utensils  ? 

A.  It  is  sheet  iron  dipped  into  melted  tin 
a  portion  of  which  adheres  to  the  surface 

262 


METALS. 


263 


as  tiij,  and  another  enters  into  the  iron  and 
alloys  with  it. 

The  ancients  are  supposed  to  have  made  use  of  tin,  and  there  is  good 
reason  for  believing  that  it  was  obtained  by  the  Phenlcians,  from  Corn- 
wall and  Spain,  at  least  1000  years  before  Christ. 

981. 

Q.  How  is  steel  made  from  iion? 

A.  The  iron  is  surrounded  with  charcoal, 
and  placed,  during  six  or  eight  days,  in  a 
furnace  intensely  heated  ;  the  carbon  unites 
with  the  iron,  and  forms  what  is  called 
'^carburet  of  iron"  (or  steel.) 

982. 

Q.  What  is  meant  by  shear  steel  ? 

A.  Shear  steel  derives  its  name  on  ac- 
count of  its  being  used  for  making  shears, 
for  dressing  woolen  cloth.  Shear  steel  is 
broken  and  welded  frequently  in  order  to 
prepare  it. 

Welded,  that  is,  hammered  together  again. 
983. 

Q.  What  is  the  white  lead,  used  for  paint  ? 

A .  It  is  prepared  by  placing  sheets  of 
load  over  earthen  pots,  which  contain  weak 
acetic  acid,  and  stand  u]3on  tan  or  dung. 
The  lead  being  corroded  with  the  acid, 
unites  with  the  carbon  and  oxygen  evolved 
from  the  dung. 


264  METALS  AND  ALLOYS. 

SECTION  II.  ALLOTS. 

984. 

Q   What  are  the  component  parts  of  the 

coins  of  the  United  States. 
A  They  are  made  oi  gold,  silver,  and  cop- 
pe?? 

90  parts  of  gold,  ^  of  silver,  and  7^  copper. 
985. 

Q.  What  are  the  component  parts  of  the 
\\lver  coins  of  the  United  States  ? 
A.  Silver  and  copper. 

90  parts  silver,  10  copper. 
986. 

Q.  What  is  jeweller's  gold  ? 

A.  An  alloy  of  gold  and  copper,  with 
silver — this  gold  is  liable  to  tarnish,  but  its 
brilliancy  can  easily  be  restored,  by  im- 
mersing the  metal  in  ammonia. 

987. 

Q.  What  is  Dutch  gold? 

A.  It  is  properly  an  alloy  of  copper  and 
zinc  ;  but  the  name  is  generally  applied  to 
the  bronze  and  copper  leaf  which  is  made  in 
Germany,  and  sold  like  gold  leaf,  in  books. 

988. 

Q.  What  is  German  silver  ? 

A.  German  silver,  or  white  copper,  some- 


ALLOTS.  265 

times  called  Argentan,  is  an  alloy  of  copper, 
zinc,  and  nickel. 

The  be«t  is  made  of  50  parts  copper,  25  zinc,  and  25  nickel. 
989. 

Q  What  is  brass  ? 

A  It  is  an  alloy  composed  of  copper  and 
tmc. 

Good  brass  contains  about  2  parts  copper,  to  1  of  zinc. 
990. 

Q.  ^h^ii^  bell  metal? 

A.  An  alloy  of  copper  and  tin.    The  pro 
portions  should  be  78  of  copper,  to  22  of 
tin.    Large  bells  contain  more  copper  than 
small  ones. 

991. 

Q.  Wliat  is  pewter  ? 

A.  An  alloy  of  tin  and  lead. 

In  the  following  proportions:  1  part  lead,  20  parts  tin. 
992. 

Q.  What  is  Britannia  metal,  such  as  coffee 
and  tea-pots,  etc.,  are  made  of? 

A.  It  is  an  alloy  of  tin  with  lead,  copper, 
antimony,  etc.,  according  to  its  quality. 

993. 

Q .  How  is  iron  galvanized  ? 

A.  By  plunging  it  into  melted  zmc; 
when  an  alloy  is  formed  on  the  surfoce, 
which  prevents  oxidation,  or  (rust,) 
23 


266      GLASS,  PORCELAIN,  EARTHENWAKE. 

994. 

Q.  What  is  common  solder  ? 

A.  Solder  is  a  mixture  of  lead  and  tin. 

Fine  solder^  2  parts  tin,  and  1  lead 
Coarse  '<      i    *<     u         4  u 


CHAP.  IL— GLASS,  PORCELAIN,  EARTHED 
WARE. 

995. 

Q.  What  is  glass  ? 

A.  Glass  is  a  mixture  of  silex  and  an 
alJcaliy  usually  the  carbonate  of  potash  or 
soda,  with  lime  or  oxide  of  lead,  according 
to  the  quality  of  glass  to  be  manufactured. 
These  substances  are  melted  together  at  a 
high  temperature,  which  expels  the  carbonic 
acid.  The  mass  is  left  to  cool,  until  it  is  in 
a  proper  state  for  working. 

996. 

Q.  How  is  glass  worked  ? 

A.  Articles  of  blown  glass,  such  as  bot- 
tles, etc.,  are  made  thus:  The  workman  has 
an  iron  tube,  five  or  six  feet  long,  with  a 
mouth  piece  of  wood,  to  prevent  the  heat  of 
the  tube  from  injuring  his  mouth ;  this  tube 
he  mserts  into  the  pasty  glass,  a,nd  collects 
a  lump  large  enough  to  form  a  bottle ;  he 
then  rolls  it  on  a  marble  slab  into  a  pear- 
shaped  ball ;  this  is  inserted  into  a  metal 


OLASS,  PORCELAIN,  EARTHENWARE.  261 


mould  which  opens  and  shuts  on  hinges, 
he  then  blows  through  the  tube  so  as  to  ex- 
pand the  cooling  glass  into  the  shape  of  the 
mould.  The  mould  is  then  opened  and  the 
bottle  is  taken  out  at  the  end  of  the  tube  ;  it 
is  then  touched  y/ith  a  rod  of  cold  iron,  which 
cracks  off  the  bottle  at  its  mouth  piece. 

997. 

Q.  How  is  plate  glass  made  ? 

A.  It  is  cast  on  a  flat  metal  table,  and 
after  careful  annealing,  it  is  ground  and 
polished  by  machinery. 

"  Annealing,^^  a  process  which  renders  glass  less  brittle  or  liable  to 
break.  This  extreme  brittleiiess  is  prevented  by  placing  the  glass  in  an 
oven,  where  it  will  cool  very  slowly.  It  requires  some  hours,  or  even  days, 
to  oool.    This  is  called  annealing. 

998. 

Q.  How  is  plate  glass  ground  ? 

A.  One  plate  of  glass  is  attached  to  a  ta- 
ble, another  smaller  one  is  firmly  fixed  in  a 
wooden  frame.  The  smaller  one  is  made 
to  move  ( )ver  the  low^er  plate  by  means  of 
machinery.  At  first,  moistened  sand  is 
thrown  between  the  plates;  as  they  become 
smoother,  wet  emery  of  different  degrees  of 
fineness  h  used,  instead  of  the  sand;  lastly 
it  is  polished  with  putty  of  tin. 

Putty  of  tin  "  is  made  thus:  1  i  is  heated  above  its  melting  point: 
it  then  oxidizes  rapidly,  becoming  <-'•  iverted  into  a  whitish  powder  used 
in  the  arts  for  polishing  under  the  n^.i}e  of  putty  powder^  or  putty  of  tin. 

9  )  9. 

Q.  For  what  purpo,-es  is  plate  glass  used  ? 


268      GLASS,  PORCELAIN,  EARTHENWARE. 


A.  For  mirrors  and  large  window  panei^ 
icoo. 

Q.  How  are  mirrors  made  ? 
A.  They  are  made  of  plate  glass,  covered 
with  an  alloy  of  mercury  and  tin. 

The  alloy  is  formed  of  30  parts  raercury,  70  tin 
1001. 

Q.  What  is  porcelain  ? 

A.  All  kinds  of  china  ware,  such  as  are 
used  for  dishes,  cups,  etc.,  are  denominated 
porcelain — some  kinds  are  much  finer  and 
more  beautiful  than  others. 

1002. 

Q.  Of  what  is  porcelain  composed  ? 

A.  The  chief  materials  used  in  its  manu- 
facture are  a  certain  clay  derived  from  de- 
composed feldspar,  calcined  flints  finely 
ground,  together  with  a  portion  of  feldspar 
reduced  to  powder. 

"  Feldspar,'*^  a  kind  of  mineral.  "  Calcined,^^  heated  i  otensely  hot  so 
M  to  crumble. 

1003. 

Q.  How  are  these  materials  mixed  to 
gether  ? 

A.  They  are  put  into  a  kind  of  mill^ 
which  is  a  large  cylindrical  vessel  or  tub, 
into  which  a  small  stioam  of  water  is  con- 
stantly suffered  to  tri(  ide,  the  mass  is  now 
ground  or  mixed  irlj  a  kind  of  pap  oi 


GLASS,  PORCELAIN,  EARTHENWARE.  269 

doLigli.  This  dough  is  kneaded  or  worked 
with  the  hands  until  the  mass  is  quite 
smooth  and  of  a  uniform  color.  It  is  now 
ready  for  moulding. 

1004. 

Q  What  is  moulding  . 

A  Forming  the  dough  or  paste  into  the 
ahape  required,  such  as  bowls,  plates,  cups, 
etc 

1005. 

Q.  How  are  these  articles  moulded  ? 

A.  The  operation  is  performed  on  a  ma- 
chine called  a  potters'  lathe.  A  small  piece 
of  the  clay  or  dough  is  placed  upon  this 
lathe,  and  owing  to  the  rapid  rotary  motion 
of  thp  machine,  the  workman  is  able  to 
shape  a  vessel  by  keeping  his  hands  con- 
stantly wet ;  he  moulds  it  to  a  proper  size 
by  means  of  pegs  and  guages.  It  is  now 
suffered  to  dry  partially ;  it  is  then  placed 
upon  another  lathe,  when  it  is  shaped  more 
evenly  and  accurately,  and  nicely  smoothed 
and  burnished  with  a  smooth  steel  surface. 
The  vessels  are  then  put  in  a  kiln  and 
baked. 

1006. 

Q.  How  long  is  porcelain  usually  baked? 
A,  It  requires  forty  hours  or  more. 
23* 


270      GLASS,  PORCELAIN,  EARTHENWARE. 

1007. 

Q.  How  is  the  gloss  given  to  our  china 
plates  ? 

A.  This  is  called  glazing.  Glaze  is  made 
in  various  ways,  according  to  the  quality  of 
the  articles  to  be  glazed. 

Gypsum,  silica,  and  a  little  porcelain  clay 
are  ground  together  and  diffused  through 
water.  Sometimes  a  little  lead  is  added. 
Each  article  is  dipped  for  a  moment  in  this 
mixture  and  withdrawn,  the  water  sinks 
into  the  substance,  leaving  the  powder 
evenly  spread  on  its  surface.  They  are 
once  more  dried,  and  put  in  a  kiln  which  is 
fired  at  an  extremely  high  temperature.  It 
is  then  finished,  unless  it  is  to  be  gilded  or 
otherwise  ornamented. 

1008. 

Q.  How  is  stoneware,  such  as  is  used  for 
jugs,  jars,  etc.,  made  ? 

A.  This  is  a  very  coarse  kind  of  porce- 
lain, made  from  clay  containing  oxide  of 
iron  and  a  little  lime. 

1009. 

Q.  How  is  stoneware  glazed  ? 

A.  By  throwing  common  salt  into  the 
heated  furnace ;  this  is  volatilized  by  the  va- 
por of  water  which  is  always  present,  and 


GLASS,  PORCELAIN,  EARTHENWARE.  271 

the  silica  of  the  clay  of  which  the  ware  is 
coiDj^osed.  This  fuses  over  the  surface  of 
the  ware,  and  gives  a  thin  but  excellent 
glaze. 

Volatilize ^''^  to  fly  off.    "  Fwses,"  melts  or  liquefies  by  heat. 
1010. 

Q.  What  is  earthenware  ? 

A.  This  is  composed  of  a  species  of  clay 
mixed  with  silica.  It  is  moulded  in  the 
same  manner  as  porcelain,  dried  and  baked 
in  a  kiln ;  after  that,  it  is  glazed  with  a  mix- 
ture which  contains  the  oxides  of  lead  and 
tin,  after  which  it  is  reheated. 

Articles  g^lnzed  with  this  mixture,  are  very  improper  for  culinary  vea 
ldl3,  aa  the  lead  in  the  glaze  is  affected  by  acids. 


PART  IV. 

ORGANIC  CHEMISTRY. 


1011. 

Q.  What  are  the  elements  which  compose 

organic  substances  generally  ? 

A.  All  organic  substances,  with  com- 
paratively few  exceptions,  are  composed  of 
carbon,  hydrogen,  oxygen  and  nitrogen. 

Sulphur  and  phosphorus  are  occasionally  associated  with  these,  anl 
also  certaiti  compounds  containing  chlorine,  iodine,  etc. 


CHAP.  I.— SUGAR. 

1012. 

Q.  Of  What  is  sugar  composed  ? 
A.  Of  carbon^  hydrogen  and  oxygen. 

1013. 

Q.  Is  sugar  a  vegetable  substance  ? 

A.  Yes  ;  it  is  found  in  the  juice  of  many 
plants  and  in  the  sap  of  several  trees ;  but 
Lt  is  extracted  in  the  greatest  abundance 
from  the  juice  of  the  sugar-cane,  which  is 
cultivated  for  that  purpose  in  our  Soutlieri) 
States. 


SUGAR. 


273 


1014. 

Q.  From  what  other  sources  is  sugar  ob- 
tained ? 

A,  From  the  sugar  maple  which  grows 
tibundaiitly  in  the  United  States,  and  ivom 
beet  root. 

The  sugar  maple  is  a  species  of  maple,  the  botanical  name  of  whicfc  it 
ttcer  saccharinum  ;  it  thrives  better  in  New  York  and  Pennsylvania  thao 
elsewhere. 

1015 

Q.  How  is  sugar  made  from  the  sugar 
cane  ? 

A.  The  cane  is  crushed,  and  the  ex- 
pressed juice  mixed  with  a  small  quantity 
of  slacked  lime,  and  heated  to  near  the 
boiling  point;  the  clear  liquid  thus  pro- 
duced is  rapidly  evaporated  in  an  open  pan, 
after  which  it  is  transferred  to  a  shallow 
vessel  and  left  to  crystallize,  during  which 
time  it  is  frequently  agitated,  in  order  to 
liinder  the  formation  of  large  crystals ;  it 
is  then  drained  from  the  syrup,  or  molasses. 
This  is  what  is  called  raw  or  Muscovado 
sugar ;  after  which  it  is  refined. 

1016. 

Q.  How  is  sugar  refined  ? 

A.  By  re-dissolving  it  in  water,  and  add- 
ing a  certain  quantity  of  albumen  in  the 
shape  of  blood  or  white  of  egg,  and  some- 


274 


SUGAK. 


times  a  little  lime-water,  and  heating  tliQ 
whole  to  the  boiling  point. 

1017. 

Q.  What  effect  has  the  albumen  on  the 
sugar  ? 

A.  It  coagulates,  and  forms  a  kind  of  net- 
work of  fibres,  which  enclose  and  separate 
from  the  liquid  all  the  impurities  suspended 
in  it. 

1018. 

Q.  What  is  the  next  process  towards 
making  sugar  ? 

A.  It  is  then  filtrated  through  charcoal, 
evaporated  and  put  into  conical  earthen 
moulds,  where  it  solidifies.  It  is  then 
drained  and  dried,  and  the  product  is  the 
ordinary  loaf  sugar. 

1019 

Q.  What  is  grape  sugar  ? 

A.  It  is  the  sugar  of  fruits,  and  is  abun- 
dantly diffused  throughout  the  vegetable 
kingdom.  It  is  called  grape  sugar,  because 
it  exists  naturally  in  the  juice  of  grapes. 


FERMENTATION. 


275 


CHAP  n  — FERMENTATION  AND  PUTRE- 
FACTION. 

SECTION  I.  FERMENTATION. 

1020. 

Q  What  is  fermentation  ? 
A.  Fermentation  is  the  change  effected  in 
he  elements  of  a  body  composed  of  carbon^ 
hydrogen  and  oxygen. 

1021. 

Q.  What  new  compounds  are  produced  by 
the  change  called  fermentation  ? 

A.  Alcohol  and  carbonic  acid,— The  alco- 
hol is  still  further  changed  (unless  the  pro- 
cess be  checked)  into  acetic  acid  or  vinegar. 

1022. 

Q.  What  are  the  elements  of  grape  sugar? 
A.  Carbon,  oxygen,  and  hydrogen,  all  in 
equal  proportions. 

1023. 

Q.  What  changes  does  sugar  undergo  by 
fermentation  ? 

A.  It  is  first  decomposed,  and  then  its 
elements  re-unite  in  different  proportions, 
producing  alcohol,  carbonic  acid,  and  water. 

OfsuGAK,  one  portion  is  alcohol;  and  another  carbonic  acid;  as  may 
>e  seen  by  the  following  table : 

Carh,  Oxy.  Hyd. 
Every  atom  of  anhydrous  sugar  contains    ...    12      12  12 

Two  atoms  of  alcohol  contain  8        4  12 

Four  atoms  of  carbonic  acid  contain   4        8  0 

12      12~^  12 

N  B.     Anliydroas  sugar,"  is  sugar  dried  at  300°. 


276     FERMENTATION  AND  PUTREFACTION. 


1024. 

Q.  How  does  sugar  form  alcohol  by  fer 
mentation  ? 

A.  Two-thirds  of  its  carbon  and  one-third 
ol*  its  oxygen  re-unite  with  the  hydrogen, 
*ind  generate  alcohol. 

1025. 

Q.  How  does  sugar  form  carbonic  acid  by 
fermentation  ? 

A.  The  remaining  one-third  of  its  carbon 
and  twO'thirds  of  its  oxygen  re-unite,  and 
generate  carbonic  acid. 

1026. 

Q.  What  becomes  of  the  alcohol  which  is 
thus  generated  by  fermentation  ? 

A.  It  mixes  with  the  water,  and  forms 
the  intoxicating  j)art  of  beer  and  wine. 

1027. 

Q.  What  becomes  of  the  carbonic  acid, 
which  is  generated  by  fermentation  ? 
A.  It  makes  its  escape  into  the  air. 

1028. 

Q.  Why  is  barley  malted  ? 

A.  Because  germination  is  produced  by  tho 
artificial  heat;  and  in  germination,  the  starch 
r)f  the  grain  is  converted  into  sngar. 

1029 

Q,  What  is  alcohol  ? 


FERMENTATION. 


277 


A.  The  spirit  of  beer  and  wine,  obtained 
by  fermentation, 

1030. 

Q.  Of  what  elements  is  aj/coM  composed? 
A  .  Of  carbon,  oxygen,  and  hydrogen 

Of  Ai/^OHOLj  4  parts  are  carbon,  2  oxygen,  and  6  hydrogen. 
1031. 

Q.  What  is  the  origin  of  the  term  proof 
npirit  7 

A.  It  IS  derived  from  the  old  method  of 
testing  spirit,  which  was  thus  :  The  spirit 
to  be  tested  was  poured  over  gunpowder,  and 
ignited ;  if  the  powder  exploded,  the  spirit 
was  said  to  be  above  proof ;  if  it  did  not  ex- 
plode, it  was  said  to  be  below  proof. 

1032. 

Q.  What  is  meant,  at  the  present  day, 
by  spirit  above  and  below  proof? 

A.  If  we  say  that  spirit  is  ten  over  proof, 
we  mean,  that  one  hundred  gallons  of  it  will 
require  ten  gallons  of  water  to  reduce  the 
spirit  to  proof  strength.  So  on  the  converse . 
if  we  say  that  spirit  is  ten  under  proof,  we 
mean  that  ten  gallons  of  water  must  be  taken 
from  the  spirit  to  raise  it  to  proof  strength. 

The  strength  of  spirit  is  now  tested  by  an  instrument  called  the  hydro 
meter. 

1033. 

Q.  What  wines  contain  the  most  spirit, 
and  what  the  least  ? 

24 


278     FERMENTATION  AND  PUTREFACTION. 


A,  Champagne  IS'  one  of  the  weakest  wines, 
then  hock,  then  sherry,  and  Port  is  one  of 
the  strongest.  Pour  glasses  of  Port  are 
nearly  equal  to  five  of  sherry. 

Champagne  contains  about  12  r)er  cent  of  alchchoi 
Hock  "        "      13  " 

Claret  «        "      16*'*     "  " 

Sherry  «        "      19  « 

Port  "        «      23^  « 

1034. 

Q.  Why  is  it  not  needful  to  put  yeast  into 
grajf?^  juice,  in  order  to  j)roduce  fermenta- 
tion? 

A.  Because  grape  juice  contains  a  suffi- 
cient quantity  of  a  nitrogenized  substance 
(like  yeast)  to  produce  fermentation. 

Nitrog-enized,  that  is,  containing  nitrogen. 
1035. 

Q.  Why  do  not  grapes  ferment,  while  they 
hang  on  the  vine  ? 

A.  Because  the  water  of  the  juice  evapo- 
rates through  the  skin,  and  allows  the 
grapes  to  shrivel  and  dry  up,  after  they  are 
ripe. 

I'ermentat.ion  cannot  occur  unless  the  sugar  be  dissolved  in  a  sufSciea 
\  ianti*y  of  water. 

1036. 

Q  What  is  gluten  ? 

A.  A  tough,  elastic  substance,  comj^osed 
of  carbon,  oxygen,  hydrogen,  and  nitrogen. 

1037. 

Q.  Does  malt  contain  gluten  ? 


FERMENTATION. 


279 


A.  Yes.    The  infusion  of  malt,  callecl 
sweet- wort''   contains  an    abundance  of 
gluten ;  and  the  yeast  (which  converts  itb 
sugar  into  alcohol)  converts  this  gluten  into 
yeast. 

1038. 

Q.  How  is  barley  malted  . 

A.  It  is  moistened  with  water ^  and  heaped 
up;  by  which  means,  great  heat  is  produced, 
which  makes  the  barley  sprout. 

(See  "  spontaneous  combustion.") 
1039. 

Q.  Why  is  not  the  barley  suflfered  to  grow 
as  well  as  sprout  ? 

A.  Because  plants  in  the  gerrn  contain 
more  sugar  than  in  any  other  state  ;  as  soon 
as  the  germ  puts  forth  shoots,  the  sugar  of 
the  plant  is  consumed,  to  support  the  shoot. 

1040. 

Q.  How  is  barley  prevented  from  shooting 
in  the  process  of  malting  ? 

A.  It  is  put  into  a  kiln,  as  soon  as  it 
sprouts,  and  the  heat  of  the  kiln  checks  or 
destroys  the  young  shoot. 

1041. 

Q.  What  is  yeast  ? 

A.  The  foam  of  beer  (or  of  some  similar 
liquor)  produced  by  fermentation. 


280     FERMENTATION  AND  PUTREFACTION. 
1042. 

Q.  Why  is  yeast  used  in  brewing  ? 

A.  Because  it  consists  of  a  substance  call* 
ed  gluten,  undergoing  putrefaction ;  in 
which  state  it  possesses  the  peculiar  pro- 
perty of  exciting  fermentation. 

If  the  gluten  were  not  in  a  putrefying  state,  it  could  not  produce  r«jer- 
mentation. 

1043. 

Q.  Why  is  yeast  needful  in  order  to  make 
malt  into  heer  ? 

A.  Because  the  presence  of  a  putrefying 
body  containing  nitrogen  is  essential,  in 
order  to  convert  sugar  into  alcohol. 

1044. 

Q.  What  effect  has  yeast  upon  the  sweet- 
wort  ? 

A.  It  causes  the  sugar  to  be  converted 
into  alcohol  and  car  bonic  acid ;  and  its  glu- 
ten  into  yeast. 

1045. 

Q.  Why  is  porter  much  darker  than  ale  or 
beer? 

A.  Because  the  malt  of  which  porter  in 
made,  is  dried  at  a  higher  temperature,  ap^d 
slightly  charred. 

Small  beer  is  a  weak  wort  fermented,  and  contains  1^  per  cent,  of  ^ 
tohol. 

Ale  is  a  stronger  wort,  and  contains  7  per  cent,  of  alcohol. 

Porter  contains  4^  per  cent,  of  alcohol. 

Brown  Stout  contains  Of  per  cent,  of  alcohol. 

Burton  Ale  contains  8^  per  cent,  of  alcohol. 

N.  B.     Wort "  is  tlie  fermentable  infusion  of  malt  or  grain. 


FERMENTATION, 


281 


1046. 

Q.  What  is  the  /ro/A  or  of  fenneiited 
liquors  ? 

Putrefying  glutinous  substances  (of  a 
nature  similar  to  yeast,)  which  rise  to  the 
smfacG  from  their  lightness. 

1047. 

Q  Why  is  beer  flat  if  the  cask  be  left  open 
too  long  ? 

A.  Because  too  much  of  the  carbonic  acid 
gas  (produced  by  fermentation)  is  sulfered 
to  escape. 

1048. 

Q.  Why  are  beer  and  porter  made  stale  by 
being  exposed  to  the  air  ? 

A.  Because  too  much  of  the  carbonic  acid 
gas  (produced  by  fermentation)  is  suffered 
to  escape. 

1049. 

Q.  Why  does  beer  turn  flat  if  the  vent  peg 
be  left  out  of  the  tub  ? 

A.  Because  the  carbonic  acid  gas  escapes 
through  the  vent  hole. 

1050. 

Q.  Why  does  milk  turn  sour  by  keeping? 

A,  Because  it  undergoes  a  fermentation  ; 
during  which  ^'lactic  acid'^  is  formed,  which 
(urns  the  milk  sour. 

The  lactic  acid  is  formed  from  the  sugar  of  milk  by  fei mentation. 

24* 


282     FERMENTATION  AND  PUTREFACTION. 
1051. 

Q.  Why  does  milk  turn  sour  in  hot  wea 
ther  much  sooner  than  in  cold  ? 

A.  Because  heat  very  greatly  accelerates 
the  process  of  fermentation ;  during  which 
lactic  acid  is  formed,  which  turns  the  milk 
sour. 

1052. 

Q.  Why  can  you  never  boil  stale  milk  with- 
out curdling  it  ? 

A.  Because  stale  milk  is  in  an  incipient 
state  of  fermentation,  which  the  heat  of 
the  fire  greatly  accelerates ;  The  lactic 
acid  which  is  formed  during  fermentation, 
mixing  with  the  casein  of  the  milk,  coagu- 
lates it. 

1053. 

Q.  Why  does  a  small  portion  of  corrosive 
sublimate  keep  paste  from  turning  sour  ? 

A.  Corrosive  sublimate  being  a  powerful 
antiseptic,  prevents  fermentation,  which  is 
the  cause  of  the  paste  turning  sour 

1054. 

Q.  What  is  bread  ? 

A.  It  is  a  kind  of  food  prepared  gene- 
rally from  the  flour  of  wheat  mixed  with  wa- 
ter to  a  dough,  and  submitted  to  the  actioii 
of  heat  to  bake.  This  kind  of  bread  is  call- 
ed mfermented  or  unleavened  bread. 


FEEMENTATION. 


283 


1055. 

Q.  What  is  leavened  bread  ? 

A.  It  is  flour  mixed  to  a  dough  with  v.  a- 
ter,  to  which  is  added  a  little  leaven,  (or 
dough  which  has  been  fermented)  or  yenjf^ 

1056. 

Q.  What  effect  has  the  yeast  on  the 
dough  ? 

A.  It  assists  in  the  fermentation  of  the 
dough,  by  which  means,  carbonic  acid  is 
generated  in  the  mass,  and  makes  the 
bread  porous  and  light.  It  is  then  placed  in 
the  oven,  and  this  gas  expanding  by  heat 
rises  the  dough  still  more,  and  puts  a  stop 
to  any  further  fermentation. 

1057. 

Q,  How  does  fermentation  make  the  dough 
rise  ? 

A.  During  fermentation,  carbonic  acid  gas 
is  evolved;  but  the  sticky  texture  of  the 
dough  will  not  allow  it  to  escape;  so  it 
forces  up  little  bladders  all  over  the  dough. 

1058. 

Q.  Why  is  new  bread  indigestible  ? 
A.  Because  the  change  called  "panary 
fermentation,''  is  not  completed. 

"  Panary,"  from  the  Latin  word  Panis  (bread  ;)  "  panary  fermentatiOA* 
liM»ons  the  fermentation  that  dough  undergoes  in  order  to  become  bread. 

The  sugar  of  the  dough  is  converted  into 


284      FERMENTATION  AND  PUTREFACTION. 

alcohol  and  carbonic  acid  by  fermentation : 
the  dough  being  adhesive  prevents  the  es- 
cape of  these  products,  till  the  mass  is 
baked;  when  the  gas  expands,  bursts 
lb  rough  the  mass,  leaving  a  number  of 
holes  or  bladders,  to  show  where  it  was 
confined. 

So  long  as  the  bread  is  warm,  the  pro- 
cess of  fermentation  is  going  on ;  and, 
therefore,  bread  should  never  be  eaten  till 
it  is  twent/j-four  hours  old. 

105 9. 

Q.  Wliy  does  baking  dough  convert  it 
into  bread  ? 

A.  When  dough  formed  of  flour,  is  baked, 
its  starch  is  changed  into  a  gum  called 
dextrin. 

A  similar  change  is  produced  upon  the 
farinaceous  portion  of  the  dough.  The 
yeast  (added  to  the  dough)  converts  part 
of  the  starch  and  sugar  into  alcohol  and 
carbonic  acid;  of  these,  the  alcohol  evapo- 
rates in  the  oven,  and  the  carbonic  acid 
forces  the  dough  into  bubbles,  in  its  eifort 
to  escape,  rendering  the  bread  light  and 
full  of  holes. 

In  100  lbs.  of  bread,  and  100  lbs,  of  dough  we  have, 

Starch,  Sugar,  Dextrin, 

In  dough,     68  lbs.  5  lbs.  Oh  100 

?n  Uread,    53^  "  3^  «<  18  m  10(7 


FERMENTATION. 


285 


Whereby  it  will  be  seen,  that  16 J  lbs.  of  starch  have  been  converted 
ilto  the  gum  called  dextrin,  by  baking. 

Dextrin  is  a  gummy  matter  similar  to  that  which  composes  the  cells  of 
Wood  (called  cellulin)  only  it  is  soluble  in  cold  water. 

Diastase  is  a  peculiar  vegetable  principle  of  malt,  extracted  bv  watefv 
which  converts  starch  into  dextrin  or  sugar. 

1060. 

Q.  Why  is  dough  placed  before  the  fire 
A.  1st. — Because  the  heat  of  the  fire  in- 
creases the  fermentation  ;  and 

2nd. — ^It  expands  the  gas,  confined  in  the 
little  bladders;  in  consequence  of  which, 
the  bladders  are  enlarged,  and  the  dough 
becomes  lighter  and  more  porous, 

1061, 

Q.  Why  will  dough  not  rise  in  cold  wea- 
ther unless  it  be  placed  near  the  fire  ? 

A.  Because  it  gets  cold  and  then  the  air 
in  the  little  bladders  condenses — the  paste 
falls — and  the  bread  becomes  close  and 
heavy. 

1062. 

Q.  Why  is  well  made  bread  full  of  holes 
or  bubbles? 

A.  Because  the  fermentation  of  the  dough 
throws  up  little  bubbles  filled  with  carbonic 
acid  gas ;  and  when  the  dough  is  baked, 
these  bubbles  are  made  permanent  in  the 
bread. 


286      FERMENTATION  AND  PUTREFACTION. 


SECTION  II.  PUTREFACTION 

1033 

Q.  What  is  the  difference,  between  fermefu 
tation  and  putrefaction  ? 

A  .  Fermentation  is  a  change  effected  in 
llie  elements  of  a  body  composed  of  car- 
bon, oxygen,  and  hydrogen,  without  nitro* 
gen.  Putrefaction  is  a  change  effected  in 
the  elements  of  a  body  composed  of  car* 
bon,  oxygen,  hydrogen,  and  nitrogen. 

1064. 

Q.  What  new  compounds  are  produced 
by  the  change  called  putrefaction  ? 

A.  The  carbon,  oxygen,  hydrogen,  and 
nitrogen,  of  the  original  substance  (being 
separated  by  decomposition)  re-unite  in  the 
following  manner.  1.  Carbon  and  oxygen 
unite  to  form  carbonic  acid.  2.  Oxygen  and 
hydrogen  unite  to  form  tvater.  3.  Hydro- 
gen and  nitrogen  unite  to  form  ammonia. 

Hartshorn  is  a  solution  of  ammonia  in  water. 

N.  B.  When  bodies  containing  sulphur  and  phosphorus  putrefy,  the 
sulphur  Oiud  phosphorus  unite  with  hydrogen,  and  form  sulphuretted  and 
pkosphuretted  hydrogen  gases. 

1065. 

Q.  What  becomes  of  these  several  pro 
ducts  of  putrefaction  ? 

A.  They  are  all  elastic  bodies,  and  es* 
cape  into  the  air. 

N  B.  Water  is  elastic  and  gaseous  when  in  the  condition  of  vapor. 


PUTREFACTION. 


287 


1066. 

Q.  What  is  the  cause  of  the  offensiv^^ 
mell  which  issues  from  putrefying  bodies  ? 

A.  The  evolution  of  ammonia^  or  of  snU 
phuretted  and  phosphuretted  hydrogen  gases ; 
all  of  which  have  pungent  and  offensive 
odors. 

1067. 

Q.  What  change  is  produced  in  gluten 

by  putrefaction  ? 

A.  Its  elements  are  loosened  from  their 
former  conditions  of  combination,  and  re- 
arranged (with  the  addition  of  oxygen  from 
the  air)  into  a  new  series. 

1068. 

Q.  Why  do  boiled  eggs  discolor  a  silver 
spoon  ? 

A.  Because  they  contain  a  small  portion 
of  sulphur,  which  unites  toith  the  silver  (for 
which  it  has  a  great  affinity)  and  tarnishes 

Ur^h  tn»  tfvhite  and  yolk  contain  sulphur— the  latter  more  abundantly. 
1069. 

Q.  What  causes  the  offensive  smell  of 
stale  hard  boiled  eggs  ? 

A.  The  hydrogen  of  the  egg  combining 
with  the  sulphur  and  phosphorus,  form  suU 


288      FERMENTATION  AND  PUTREFACTION. 

phuretted  and  phosphuretted  hydrogen  ;  both 
of  which  gases  have  an  offensive  odor. 

Of  an  ecrcr  55  parts  are  carbon,  IG  nitrogen.  7  hydrogen,  and  the  re^ 
maining  '22  are  oxygen,  phosphorup,  and  sulphur. 

1070. 

Q.  Decaying  vegetables  are  first  of  a 
brownish  tint,  why  do  they  afterwards  turn 
of  a  blackish  color  ? 

A.  Because  the  hydrogen  of  the  decaying 
vegetables  is  separated  from  the  mass  by 
the  process  of  decay,  and  leaves  a  larger 
proportion  of  carbon  behind. 

Vegetable  fibre  contains  52^-  per  cent  of  carbon. 
When  partially  decayed  54     "     *'  " 
When  black  with  decay  56     "     "  " 

1071. 

Q.  Why  are  decaying  vegetables  always 
moist? 

A.  Because  the  hydrogen  and  oxygen  of 
the  vegetables,  are  given  up  by  decay,  and 
form  into  water. 

Decaying  vegetables  combine  into  the  following  new  forms  :  1st. — The 
oxygen  and  hydrogen  form  into  water;  and  2nd. — The  carbon  unites 
with  the  oxygen  of  the  air,  and  produces  carbonic  acid  gas. 

1072. 

Q.  Why  does  meat  putrefy  sooner  in  hot 
damp  weather,  than  in  cold  ? 

A.  Because  the  carbon  of  the  meat 
unites  with  the  oxygen  of  the  air  more 
readily  when  hot  than  cold  ;  and 

Because  the  damp  deposited  on  the  sur- 
face of  the  meat,  is  of  itself  one  of  the 


PUTREFACTION. 


289 


compounds  of  putrefaction,  and  leaves  an 
excess  of  hydrogen  in  the  meat. 

Thus  the  original  proportions  and  com* 
Li  nations  of  the  meat  are  altered  and  de- 
composed. 

Patrefac lion  is  simply  the  decomposition  of  the  original  elements,  and 
leir  '  e-uniou  in  a  new  order.   The  new  order  i^  as  follows  : — 
1st  — Carbon  and  oxygen  unite  to  form  carboni?  acid ; 
2nd. — Hydrogen  and  oxygen  "         "  water; 
3rd. — Hydrogen  and  nitrogen  "         "  ammonia. 
N  B.  Carbon  unites  with  oxygen  with  a  readiness  proportioned  to  itt 
heat ;  when  red  hot,  the  combination  is  most  easily  effected. 

The  chief  reason  why  salt  preserves  meat  is  because  it  absorbs  the  wa» 
.er  from  it,  and  deprives  it  of  hydrogen. 

1073. 

Q.  Why  does  meat  putrefy  most  rapidly 
in  very  changeable  weather  ? 

A.  Because  moisture  is  more  freely  de- 
posited on  the  meat  in  very  changeable 
weather ;  and  this  moisture  is  a  chief  com- 
pound of  putrefaction. 

1074. 

Q.  How  can  the  taint  of  meat  be  re- 
moved ? 

A.  Either  by  washing  with  pyroligneous 
acid — or  by  covering  it  for  a  few  hours 
with  common  charcoal — or  by  putting  a  few 
lumps  of  charcoal  into  the  water  in  which  it 
is  boiled, 

,1075. 

Q.  Why  do  these  things  destroy  the 
frfint  of  meat  ? 

25 


290      FERMENTATION  AND  PUTREFACTION. 

A.  Because  they  combine  Avith  the  putre^ 
tent  particles,  and  neutralize  their  offensive 
taste  and  smell. 

1076. 

Q.  Why  does  stagnant  water  pvtrefy? 
A.  Because  leaves,  plants,  insects,  etc., 
are  decomposed  in  it. 

1077. 

Q.  Why  is  stagnant  water  full  of  vjorms, 
eels,  etc? 

A.  Because  numberless  insects  lay  their 
eggs  in  the  leaves  and  plants  floating  on  the 
surface ;  these  eggs  are  soon  hatched,  and 
produce  swarms  of  worms,  eels,  and  in- 
sects 

1078. 

Q.  Why  is  flowing  water  free  from  these 
impurities  ? 

A.  1st. — Because  the  motion  of  running 
water  prevents  fermentation  ; 

2nd. — It  dissolves  the  putrid  substancei 
which  happen  to  fall  into  it :  and 

3rd  — It  casts  on  the  bank  (by  its  cur» 
rviut)  such  substances  as  it  cannot  dissolve. 

1079. 

Q.  Birds,  after  they  are  killed,  keep 
longer  in  their  feathers,  tlian  when  they  ai^ 
plucked.    Why  is  tliis 


PUTREFACTION. 


291 


A.  Because  the  feathers  prevent  the  air 
or  damp  from  getting  so  readily  to  the  bird, 
to  produce  decay. 

1080. 

Q.  Why  does  unseasoned  wood  decay  much 
raore  rapidly  than  wood  well  seasoned  ? 

A.  Because  the  albumen  which  the  sap 
contains  produces  a  species  of  fermenta- 
tion ;  during  which  the  cellulin  and  lig- 
neous matter  of  the  wood  are  turned  into 
carbonic  acid  and  water. 

Albumen,"  a  substance  resembling  the  white  of  an  egg. 

"Cellulin,"  the  substance  which  composes  the  cells  of  wood,  as  wax 
composes  the  cells  of  a  honey  comb. 

*'  Ligneous  matter,"  or  vegetable  fibre,  is  the  hard  or  woody  part  of 
wood. 

1081. 

Q.  Why  is  wood  placed  in  a  stream  of 
running  water  to  season  it  ? 

A.  Because  the  running  water  washes 
away  the  sap ;  and  thus  prevents  fermenta-' 
lion  and  decay. 

1082. 

Q.  Why  will  solutions  of  salts  prevent 
the  decay  of  wood  steeped  therein? 

A.  Because  the  salts  unite  with  the 
albumen  of  the  sap,  coagulate  it,  and  prevent 
foraientation. 


292     COMPONENTS  OF  THE  ANIMAL  BODY. 


CHAP.  Ill  —COMPONENTS  OF  THE  ANfMAL 
BODY. 
1083. 

Q.  What  is  albumen  ? 

A.  Tlie  serum,  or  fluid  portion  of  the 
blood,  (which,  after  exposure  to  the  air,  is 
separated  from  the  more  solid  part)  the 
vitreous  and  crystalline  humors  of  the  eye,  the 
hrain,  spinal  marrow,  and  nerves,  all  contain 
albumen. 

It  exists  most  abundantly,  and  in  its 
purest  natural  state,  in  the  white  of  an  egg  ; 
from  whence  it  derives  its  name  {album  ovi) 
which  is  the  Latin  for  the  white  of  an  egg. 

1084. 

Q.  Why  will  milk  burn  very  easily,  when 
boiled ;  water  will  not  do  so  ;  explain  this? 

A.  1st. — Because  milk  contains  solid  or- 
ganic substances,  capable  of  burning;  which 
water  does  not ;  and 

2nd. — Because  the  heat  of  the  fire  coagu- 
lates the  albumen  of  the  milk,  which  falls  1c 
the  bottom,  and  adheres  to  the  boiler. 

1035. 

Q.  Why  are  lamb  and  veal  more  tcndei 
than  beef  and  mutton  ? 

A.  Because  they  contain  more  albumen, 
and  less  muscular  fibre. 


Aibumen  is  a  substance  like  the  white  of  an  egg 


COMPONENTS  OF  THE  ANI^UL  BODY.  293 


10B6. 

Q.  Why  do  lamb  and  veal  taint  more  quick- 
ly than  beef  and  mutton  ? 

A.  Because  they  contain  a  large  quantit}^ 
of  albumen,  which  is  very  liable  to  putrefac- 
tion. 

1087. 

Q.  Why  is  meat  tough  which  has  been 
boiled  too  long  ? 

A.  Because  the  albumen  becomes  hard  like 
the  white  of  a  hard  boiled  egg. 

The  best  way  of  boiling  meat  to  make  it  tender,  is  thus  :  Pat  yo  jr  joint 
in  very  brisk  boilin<?  water;  after  a  few  minutes  add  a  little  cold  water. 
The  boiling  water  will  fix  the  albumen,  wliich  will  prevent  the  water  from 
Boaking  into  the  meat — keep  all  its  juices  in — and  prevent  the  muscular 
fibre  from  contracting.  The  addition  of  cold  water  will  secure  the  cook- 
ing of  the  inside  of  the  meat,  as  well  as  of  the  surface. 

1088. 

Q.  Why  is  meat  always  tough,  if  it  be  put 
into  the  boiler  before  the  water  boils  ? 

A.  Because  the  water  is  not  hot  enough 
to  coagulate  the  albumen  between  the  mus- 
cular fibres  of  the  meat,  which,  therefore, 
runs  into  the  water,  and  risej?  to  the  surface 
as  a  scum. 

1089. 

Q,  Why  is  the  flesh  of  old  animals  tough  ? 
A.  Because  it  contains  very  littl^^  albumen^ 
and  much  muscular  fibre. 

1090. 

Q.  Is  salted  meat  as  nutritious  fresh 
meat  ? 

25* 


294     COMPONENTS  OF  THE  ANIMAL  BODY 

A .  No  ;  because  the  albumen  of  the  meat 
is  separated  from  the  flesh  by  the  brine  ; 
ns  well  as  the  alkaline  phosphates,  and  some 
other  substances  of  great  value. 

I'hDPphates  are  alkaline  and  nnineral — Alkaline  phosphates  are  phosphth 
\c  acid  combined  with  some  alkali^  such  as  soda,  potasii,  magnesia,  etc. 

Alhumen  of  ti  e  meat  " — a  substance  resembling  the  white  of  an  egg^ 
frhich  lies  between  the  muscular  fibres  of  all  flesh,  and  niakes  the  meat 
ender. 

The  alkaline  phosphates  of  meat"  are  such  as  these:  the  phosphate 
Df  soda,  the  phosphate  of  potash,  and  the  phosphate  of  magnesia,  which  ara 
extracted  from  the  meat  by  the  acid  reaction  of  the  brine. 

1091. 

Q.  Why  does  salt  preserve  meat? 

A.  1st. — Because  it  removes  the  water 
contained  in  the  animal  fibre  ;  absorbing  it, 
and  leaving  the  meat  dry. 

2nd. — Salt  is  comjoosed  of  chlorine  and 
sodium ;  the  chlorine  of  the  salt  takes  up 
the  hydrogen  of  the  meat  as  it  is  given  off, 
and  prevents  the  offensive  taste  and  smell 
of  decay : 

3rd. — Brine  draws  away  the  albumen  from 
between  the  muscular  fibres,  which  is  very 
subject  to  putrefaction  : 

4  th. — The  salt  unites  with  the  muscular 
fibre,  and  makes  a  new  chemical  compound 
much  less  subject  to  decay ;  and 

5th. — It  keeps  the  air,  flies,  etc.,  from 
the  meat. 

1092. 

Q.  Is  albumen  found  only  in  animals? 


cojviponents  of  the  anmal  body.  295 


A.  No ;  it  abounds  also  in  vegetables.  It 
makes  the  chief  bulk  of  some  seeds,  as 
grapes,  corn,  etc. 

1093. 

Q.  What  is  fibririe  ^ 

A.  It  is  a  compound  which  abounds  in 
f)oth  animal  and  vegetable  substances — the 
chief  part  of  muscular  flesh  is  formed  of 
fibrine.  It  also  exists  in  chyle,  and  enters 
into  the  composition  of  the  blood. 

1094, 

Q.  What  is  caseine  ? 

A.  It  exists  in  millc,  and  constitutes  the 
greater  part  of  cheese  made  from  skimmed 
milk. 

1095. 

Q.  Does  caseine  exist  also  in  vegetables  ? 

A.  It  is  found  in  peas,  beans,  etc.  They 
are  crushed,  mixed  with  water,  and  then 
strained.  In  this  way  the  caseine  is  pro- 
cured, which  has  all  the  characteristics  of 
skimmed  milk. 

1096. 

Q.  What  is  Gelatine  ? 

A.  It  is  a  jelly-like  substance,  formed  by 
boiling  animal  membranes,  skin,  and  even 
bones.  It  does  not  exist  in  its  natural  state 
in  the  animal  system,  but  is  easily  produced 


296     COMPONENTS  OF  THE  ANIMAL  BODY. 

by  means  of  hot  water.    The  well  known 
substance  called  isinglass,  and  also  calves^  feet 
jelly,  are  familiar  examples  of  gelatine 
Glue  is  a  kind  of  gelatine  dried  in  the  air. 

1097. 

Q.  Why  does  the  use  of  salt  beef  produce 
scurvy  ? 

A.  Because  the  soluble  salts  are  removed 
from  the  beef  by  brine  ;  in  consequence  of 
which,  it  cannot  restore  to  the  human  sys- 
tem those  salts,  which  are  essential  to  pre- 
serve the  blood  in  a  healthy  state. 

1098 

Q.  Why  does  the  use  of  vegetables  gene- 
rally prevent  scurvy  ? 

A.  Because  they  contain  the  soluble  salts 
removed  from  the  beef  by  brine  ;  which, 
oeing  restored  by  the  vegetables,  preserve 
the  blood  in  a  healthy  state. 

1099 

Q.  Whv  is  lime-juice  a  perfect  cure  for 
scurvy  ? 

A.  Because  it  contains  the  very  salts,  re- 
moved from  the  beef  by  the  action  of  the 
brine  ;  namely,  alkaline  phosphate, — and 
sulphate,  chloride,  and  phosjohate  of  lime. 

Alkaline  phosphates  "  are  such  as  these  r—pbosphate  of  so(h,  pho*. 
phjile  of  potash,  and  phosphnteof  magnesia  ;  that  is,  soda,  polag.'i,  oi  nmg 
Te«ia,  ill  conibin  itioii  with  pho«phoric  acid. 


ANIINIAL  HEAT. 


297 


CHAP.  IV.— ANIMAL  HEAT. 

1100. 

Q.  What  is  the  cause  of  animal  heat  ? 

A.  Animal  heat  is  produced  by  the  corrh 
hnstion  of  hydrogen  and  carbon  in  the  capillary 
vessels. 

1101. 

Q.  How  do  hydrogen  gas  and  carbon  get 
into  these  very  small  vessels? 

A.  The  food  we  eat  is  converted  info  blood; 
and  blood  contains  both  hydrogen  and  carbon. 

1102. 

Q.  Why  is  every  part  of  the  body  warm  ? 

A.  Because  the  capillary  vessels  run 
through  every  part  of  the  human  body,  and 
the  combustion  of  blood  takes  place  in  the 
capillary  vessels. 

1103. 

Q.  What  are  the  capillary  vessels? 

A.  Vessels  as  small  as  hairs  running  all 
over  the  body ;  they  are  called  capillary  from 
the  Latin  word  ^^capillaris/'  (like  a  hair.) 

1104. 

Q.  Do  these  capillary  vessels-  run  all  over 
the  human  body  ? 

A.  Yes.  Wlienever  blood  flows  from  a 
woundy  some  vein  or  vessel  must  be  divided; 
and,  as  you  can  bring  blood  from  any  par/ 


298 


ANIMAL  HEAT 


of  the  body  by  a  very  slight  wound,  these 
little  vessels  must  run  through  every  part 
of  the  human  frame. 

1105. 

Q.  How  does  combustion  take  place  in  the 
capillary  vessels  ? 

A.  The  carbon  of  the  blood  combines  with 
the  oxygen  of  the  air  we  breathe^  and  forms 
into  carbonic  acid  gas. 

1106. 

Q.  What  becomes  of  this  carbonic  acid  gas 
formed  in  the  human  blood  ? 

A.  The  lungs  throw  off  almost  all  of  it 
into  the  air,  by  the  act  of  respiration. 

1107. 

Q.  Does  the  heat  of  the  human  body  arise 
from  the  same  cause  as  the  heat  of  fire  ? 

A.  Yes,  precisely.  The  carbon  of  the 
blood  combines  with  the  oxygen  of  the  air  in* 
haled,  and  produces  carbonic  acid  gas,  which 
is  attended  with  combustion. 

1108. 

Q.  J f  animal  heat  is  produced  by  cc/mbtiS' 
(ion,  why  does  not  the  human  body  burn  u]) 
like  a  coal  or  candle  ? 

A.  It  actually  does  so.  Every  muscle, 
nerve,  and  organ  of  the  body  actually  wastes 
may  like  a  burning  candle  ;  and,  (being  re- 


ANIMAL  HEAT. 


299 


duced  to  air  and  ashes)  is  rejected  from  the 
system  as  useless. 

1109. 

Q.  If  every  bone,  muscle,  nerve,  and  or- 
gan, is  thus  consumed  by  combustion,  why 
is  not  the  body  entirely  consumed  ? 

A.  It  would  be  so,  unless  the  parts  de- 
stroyed were  perpetually  renewed  ;  but,  as  a 
lamp  will  not  go  out,  so  long  as  it  is  sup- 
plied  vjifh  fresh  oil,  neither  will  the  body  be 
consumed,  so  long  as  it  is  supplied  with  suffi- 
cient food. 

1110. 

Q.  What  is  the  principal  difference  be- 
tween the  combustion  of  a  fire  or  lamp,  and 
that  of  the  human  body  ? 

A.  In  the  human  body,  the  combustion  is 
affected  at  a  much  lower  temperature  ;  and  is 
carried  on  more  slowly,  than  it  is  in  a  lamp 
or  fire. 

1111. 

Q  What  causes  the  heat  of  our  Dwn 
hody  ? 

A.  The  caibon  of  our  blood  combines  with 
the  oxygen  of  the  air  inhaled,  and  produces 
carbonic  acid  gas ;  w^hich  evolves  heat  in  a 
way  similar  to  burning  fuel. 


800 


ANIMAL  HEAT. 


1112. 

Q  Why  do  oxygen  and  carbon  so  readil;^ 
unite  in  the  blood  ? 

A.  Because  the  atoms  of  carbon  are  sn 
^[losely  oitraded  by  the  other  materials  of 
Ihc  blood,  that  they  unite  very  readily  with 
ilie  oxygen  of  the  air  inhaled. 

1113. 

Q.  Is  carbonic  acid  wholesome  ? 

A.  No;  it  is  fatal  to  animal  life;  and 
(whenever  it  is  inhaled)  acts  like  a  narcotic 
poison — producing  drowsiness,  which  some- 
times ends  in  death.  • 

1114. 

Q.  How  is  it  that  carbon  can  be  made  to 
burn  at  so  lov)  a  temperature  in  the  human 
l)ody  ? 

A.  Because  the  carbon  in  the  blood  is 
reduced  to  very  minute  particles  ;  and  these 
particles  are  ready  to  undergo  a  rapid 
change  as  soon  as  oxygen  is  supplied. 

1115. 

Q  Why  are  very  poor  people  instinctively 
averse  to  ventilation  ? 

A.  1st. — Because  ventilation  increases  the. 
oxygen  of  the  air — the  combustion  of  food — 
and  the  cravings  of  appetite  ;  and 

2nd. — Ventilation  cools  the  air  of  ow 


ANIMAL  HEAT. 


301 


rooms;  to  poor  people,  therefore,  who  are 
ill  clad,  the  warmth  of  an  ill- ventilated 
a^partment  is  agreeable. 

1116. 

Q .  Why  are  the  ill-clad  also  instinctively 
averse  to  cleanliness  ? 

A.  Because  dirt  is  warm,  (thus  pigs,  who 
love  warmth,  are  fond  of  dirt ;)  to  those, 
therefore,  who  are  very  ill-clad,  the  warmth 
of  dirt  is  agreeable. 

1117. 

Q.  Why  does  flannel,  etc.,  make  us  warm? 

A.  Flannel  and  warm  clothing  do  not 
make  us  warm,  but  merely  prevent  our  body 
from  becoming  cold. 

1118. 

Q.  How  does  flannel,  etc.,  prevent  our 
body  from  becoming  cold  ? 

A.  Flannel  (being  a  bad  conductor)  will 
neither  carry  off  the  heat  of  our  body  into  the 
cold  air,  nor  suffer  the  cold  of  the  air  to  come 
in  contact  with  our  warm  body  ;  and  thus  it  is, 
that  flannel  clothing  keeps  us  warm 

1119, 

Q.  Why  are  frogs  and  fl^hes  cold-blooded 
animals? 

A.  Because  they  consume  very  little  air; 
and,  without  a  plentiful  supply  of  air.  com* 
20 


S02 


ANIMAL  HEAT. 


bustioi]  is  too  slow  to  generate  much  animal 
licat. 

1120. 

Q.  Why  is  a  dead  body  cold  ? 

A.  Because  air  is  no  longer  conveyed  tti 
the  lungs,  after  respiration  has  ceased ;  and, 
therefore,  animal  heat  is  no  longer  generated 
by  combustion. 

1121. 

Q.  Why  do  we  need  warmer  *  clothing  by 
night  than  by  day  ? 

A.  1st. — Because  the  night  is  generally 
colder  than  the  day  ;  and 

2nd. — Our  bodies  are  colder  also ;  because 
we  breathe  more  slowly^  and  our  animal 
combustion  is  retarded. 

1122. 

Q.  Why  do  we  perspire  when  very  hot  ? 

A.  The  pores  of  the  body  are  like  the  safe- 
ty valves  of  a  steam-engine  ;  when  the  heat 
of  the  body  is  very  great,  some  of  the  com- 
bustible matter  of  the  blood  is  thrown  off 
111  perspiration  ;  and  the  heat  of  the  body 
kept  more  temperate. 

1123. 

Q.  Why  does  running  make  us  warm  ? 
A.  Because  we  inhale  air  more  rapidly 
when  we  run,  and  cause  the  blood  to  pass 


ANIMAL  HEAT. 


303 


more  ra2:>idly  through  the  lungs  in  contact 
with  it.  Running  acts  upon  the  capillary 
vessels  as  a  pair  of  bellows  on  a  common  ^r^. 

1124. 

Q.  Why  does  inhaling  air  rapidly  make, 
the  body  feel  warm  ? 

A.  Because  more  oxygen  is  introduced  into 
the  body.  In  consequence  of  which,  the 
combustion  of  the  blood  is  more  rapid — the 
blood  itself  more  heated — and  every  part  of 
the  body  is  made  warmer. 

1125. 

Q.  How  does  the  combination  of  oxygen 
with  the  blood  produce  animal  heat  ? 

A.  The  principal  element  of  the  blood  is 
carbon  ;  and  this  carbon  (combining  with 
the  oxygen  of  the  air  inhaled)  produces  car- 
bonic acid  gas,  in  the  same  way  as  burning 
fuel. 

1126. 

Q.  What  becomes  of  the  nitrogen  of  the 
air,  after  the  oxygen  enters  the  blood  ? 

A.  It  is  thrown  out  from  the  lungs  im 
changed,  by  the  act  of  breathing;  to  be 
again  mixed  with  oxygen  and  converted  into 
common  air. 

1127. 

Q.  Can  you  explain  how  we  breathe  ? 


304 


ANIMAL  HEAT. 


A.  By  a  muscular  action^  we  make  an  en 
larged  space  in  the  chest;  the  pressure  of  the 
external  atmosphere  forces  air  into  this 
space,  so  as  to  fill  it.  By  a  second  muscular 
fiction  the  lungs  are  compressed,  and  the  air 
forced  out  and  escapes.  The  air  whicl) 
escapes  is  chiefly  nitrogen. 

1128. 

Q.  Why  does  the  vitiated  air  (after  the 
oxygen  has  been  absorbed)  come  out  of  the 
mouthy  and  not  sink  into  the  stomach  ? 

A.  Because  a  mechanical  provision  is 
made  in  the  upper  part  of  the  windpipe  and 
gullet  for  this  purpose. 

N.  B.  The  lungs  are  a  holloiv,  spungy  mass,  capable  of  confining  air, 
and  of  being  dilated  by  it.  They  are  so  situated  in  the  thorax  (or  chest,) 
that  tlie  air  must  ent^r  into  ihem,  whenever  the  cavities  of  the  thorax  are 
enlarged.  The  process  of  breathing  is  performed  thus  :  When  we  inhale, 
the  thorax  {or  chest)  is  expanded  ;  in  consequence  of  which,  a  vacuum  is 
formed  round  the  lungs^  and  heavy  external  air  instantly  enters  (through 
the  mouth  and  throat)  to  supply  this  vacuum. 

When  we  exhale,  the  thorax  contracts  again  ;  in  consequence  of  which, 
it  can  no  longer  contain  the  same  quantity  o(  air  as  it  did  before;  and  some 
of  it  is  necessarily  expelled.  When  this  expulsion  of  air  takes  place,  the 
lun&:s  and  muscular  fibres  of  the  wind-pipe  and  gullet  contract  in  order  to 
assist  the  process. 

1129. 

Q.  If  (both  in  combustion  and  respira- 
tion) the  oxygen  of  the  air  is  consumed,  and 
the  nitrogen  rejected — ^Why  are  not  the  pro* 
portions  of  the  air  destroyed  ? 

A.  Because  the  under  surface  of  vegetable 
leaves  (during  the  day)  gives  out  oxygen ; 


ANIMAL  HEAT. 


305 


and  thus  restores  to  the  air  the  very  ele- 
ment of  which  it  has  been  deprived. 

1130. 

Q.  Whence  do  leaves  obtain  the  oxygen 
whicL  they  exhale  ? 

A.  From  the  carbonic  acid  absorbed  by 
the  roots  from  the  soil,  and  carried  to  the 
leaves  by  the  rising  sap. 

N.  B.  Carbonic  acid  (it  must  be  remembered)  is  a  compound  of  carbon 
and  oxygen. 

1131. 

Q.  How  do  plants  contrive  to  absorb  car- 
bonic acid  from  the  soil  ? 

A.  It  rises  (by  capillary  attraction) 
through  the  small  fibrous  roots,  after  it  has 
been  dissolved  in  the  soil  by  water. 

1132. 

Q.  If  leaves  throw  off  the  oxygen  of  the 
carbonic  acid,  what  becomes  of  the  carbon. 

A.  It  is  retained  to  give  firmness  and 
solidity  to  the  plant  itself. 

1133. 

Q.  Show  how  God  has  made  animal  life 
dei)endent  on  that  of  vegetables  ? 

A.  Animals  require  oxygen  to  keep  them 
alive,  and  draw  it  from  the  air  by  inspira- 
tion :  The  under  surface  of  leaves  gives  otii 
oxygen  ;  and  thus  supplies  the  air  with  the 
very  gas  required  for  the  use  of  animals. 
26* 


306 


ANIMAL  HEAT. 


1134. 

Q.  Show  how  God  has  made  vegetable  lile 
dependent  on  that  of  animal. 

A.  Plants  require  carbonic  acid,  which  is 
tlmr  principal  food ;  and  all  animals  exhale 
(ho  same  gas  from  their  lungs.  Thus  plants 
supply  animals  with  oxygen,  and  aiimols 
supply  plants  with  carbonic  acid. 

SECTION  I.  FOOD, 

1135. 

Q.  What  is  fuel  of  the  body  ? 

A.  Food  is  the  fuel  of  the  body.  The 
carbon  of  the  food,  mixing  with  the  oxygen 
of  the  air,  evolves  heat,  in  the  same  way 
that  a  fire  or  candle  does. 

1136. 

Q.  How  is  food  converted  into  blood  ? 

A.  After  it  is  swallowed,  it  is  dissolved 
in  the  stomach  into  a  grey  pulp,  called 
Chyme  ;  it  then  passes  into  the  intestines, 
and  is  converted  by  the  "bile"  into  a  milky 
substance,  called  chvle. 

1137. 

Q.  What  becomes  of  the  milky  substance 
called  chyle  ? 

A.  It  is  absorbed  b}^  the  vessels  called 
^'lacteals,^^  and  poured  into  the  veins  on  the 
kft  side  of  the  neck. 


FOOD. 


307 


1138. 

Q ,  Wliat  becomes  of  the  chyle,  aftei  it  is 
poured  into  the  veins  ? 

A.  It  mingles  with  the  bloody  and  is  itself 
converted  into  blood  also, 

1139. 

Q.  How  does  the  oxygen  we  inhale  mingle 
with  the  blood  ? 

A.  The  oxygen  of  the  air  mingles  with 
the  blood  in  the  lungs,  and  converts  it  into 
a  bright  red  color. 

1140 

Q.  How  does  oxygen  convert  the  color  of 
blood  into  a  bright  red  ? 

A.  The  coloring  matter  of  the  blood  is 
formed  by  very  minute  globules  floating  in 
it ;  the  oxygen  (uniting  with  the  coats  oj 
these  globules)  makes  them  milky — and  the 
dark  coloring  matter  of  the  blood  (seen 
through  this  milky  coat)  appears  of  a  bright 
red. 

Exp. — If  you  put  some  dark  venous  blood  into  a  milky  ^lass,  and  hold  it 
up  towards  the  light,  it  will  appear  of  a  bright  florid  color  like  artenal 
blood. 

1141. 

Q.  What  color  is  the  blood  before  it  is 
oxidized  in  the  lungs  ? 

A.  A  dark  purple.  The  oxygen  turns  it 
to  a  blight  red. 

Oxidized,  that  is,  impregnated  with  oxygen. 


308 


ANBIAL  HEAT. 


1142. 

Q.  Why  are  persons  so  pale,  who  live  iu 
dose  rooms  and  cities? 

A .  Because  the  blood  derives  its  redness 
from  the  oxygen  of  the  air  inhaled ;  but,  as 
the  air  in  close  rooms  and  cities  is  not  fresh, 
it  is  deficient  in  oxygen,  and  cannot  turn  the 
biOod  to  a  beautiful  bright  red. 

1143. 

Q.  Why  are  persons,  who  live  in  the  open 
air  and  in  the  country,  of  a  ruddy  com 
plexion  ? 

A.  Because  they  inhale  fresh  air  which 
has  its  full  proportion  of  oxygen  ;  and  the 
blood  derives  its  bright  red  color  from  the 
oxygen  of  the  air  inhaled. 

1144. 

Q.  Why  is  not  the  air  in  cities  so  fresh  as 
that  in  the  country  ? 

A.  Because  it  is  impregnated  with  the 
breath  of  its  numerous  inhabitants,  the  odor 
of  its  sewers,  the  smoke  of  its  fires,  and  many 
other  impurities. 

1145. 

Q.  Why  do  we  feel  lazy  and  averse  to 
activity  in  very  hot  weather? 

A.  1st. — Because  muscular  activity  in- 


FOOD. 


309 


creases  the  heat  of  the  body,  by  quickening 
the  respiration;  and 

2nd. — The  food  we  eat  in  hot  weather 
(not  being  greasy)  naturally  abates  our  dry 
sire  for  bodily  activity. 

1146 

Q.  Why  are  the  Esquimaux  so  passion- 
ately fond  of  train  oil  and  whole  blubber  ? 

A.  Because  oil  and  blubber  contain  large 
quantities  of  carbon  and  hydrogen,  which  are 
exceedingly  combustible ;  and,  as  these 
people  live  in  climates  of  intense  cold,  the 
heat  of  their  bodies  is  increased  by  the 
greasy  nature  of  their  food. 

1147. 

Q.  Why  do  we  like  strong  meat  and  greasy 
food  when  the  weather  is  very  cold  ? 

A.  Because  strong  meat  and  grease  con- 
tain large  portions  of  carbon  and  hydrogen  ; 
which,  (when  burned  in  the  blood)  produce 
a  larger  amount  of  heat  than  any  other  kind 
of  food. 

1148. 

Q.  Why  do  persons  eat  more  food  in  cold 
weather  than  in  hot  ? 

A.  Because  the  body  requires  more  fuel 
in  cold  weather  to  keep  up  the  same  amount  of 
mimal  heat;  and  as  we  put  more  coals  on  a 


SIO 


ANIMAL  HEAT. 


fire  on  a  cold  day,  to  keep  our  room  warm , 
so  we  eat  more  food  on  a  cold  day,  to  keep 
our  body  warm 

1149. 

Q  Why  do  we  like  fruits  and  vegetables 
most  in  hot  weather  ? 

A.  Because  they  contain  less  hydrogen 
and  carbon  than  meat ;  and,  therefore,  pro- 
duce both  less  blood,  and  blood  of  a  less  com 
hustiblc  nature. 

1150. 

Q.  Why  do  we  feel  a  dislike  to  strong 
meat  and  greasy  food  in  very  hot  weather  ? 

A.  Because  strong  meat  and  grease  con- 
tain so  much  carbon  and  hydrogen,  that  they 
would  make  us  intensely  hot;  we  therefore, 
instinctively  refuse  them  in  hot  weather. 

1151. 

Q.  Why  do  the  inhabitants  of  tropical 
countries  live  chiefly  upon  rice  and  fruit  ? 

A.  Because  rice  and  fruit  (by  digestion) 
are  m^ainly  converted  into  water;  and  hy 
tooling  the  blood)  prevent  the  tropical  heat 
from  feeling  so  oppressive. 

1152. 

Q.  Why  is  the^  blood  of  a  less  combus- 
tible nature,  if  we  live  chiefly  upon  fruits 
and  vegetables? 


HUNGER. 


311 


A.  Because  fruits  and  vegetables  supply 
die  blood  with  a  very  large  amount  of  wa- 
ter; which  is  not  combustible,  like  the  car- 
hon  and  hydrogen  of  strong  meat. 

1153. 

Q.  How  do  fruits  and  vegetables  cool  the 
hlood^ 

A.  1st. — They  diminish  the  amount  of 

carbon  and  hydrogen  in  the  blocxJ,  which  are 
the  chief  causes  of  animal  heat;  and 

2nd. — They  supply  the  blood  with  a 
large  amount  of  water,  which  exudes  through 
the  skiUy  and  leaves  the  body  cool. 

SECTION  II.  HUNGER, 

1154. 

Q.  Why  does  cold  produce  hunger  ? 

A.  1st. — Because  the  air  contains  more 
oxygen  in  cold  weather;  and,  therefore, 
fires  burn  more  fiercely,  and  animal  combustion 
is  more  rapid ;  and 

2nd. — As  we  are  more  active  in  cold 
w  Bather,  our  increased  respiration  acts  like 
a  pair  of  bellows  on  the  capillary  combus- 
tion 

1155. 

Q.  AVhy  does  rapid  digestion  produce  a 
-^.raving  appetite? 


312 


ANIMAL  HEAT, 


A.  This  is  a  wise  providence  to  keep  our 
bodies  in  health  ;  they  give  notice  (by  hun- 
ger) that  the  capillary  fires  need  replenishing, 
m  order  that  the  body  itself  may  not  be 
consumed 

1156. 

Q.  Why  do  we  feel  a  desire  for  activity 
in  cold  weather. 

A.  1st. — Because  activity  increases  the 
warmth  of  the  body,  by  fanning  the  combus- 
tion of  the  blood  ;  and 

2nd. — The  strong  food  we  eat  creates  a 
desire  for  muscular  exertion. 

1157. 

Q.  Why  does  reading  aloud  make  us  feel 
hungry ? 

A.  Because  it  increases  respiration;  and 
as  more  oxygen  is  introduced  into  the  lungs, 
our  food- fuel  is  more  rapidly  consumed. 

1158. 

Q.  Why  do  we  feel  less  hungry  in  the 
night  than  in  the  day  ? 

A.  Because  we  breathe  more  slowly  during 
sleep ;  therefore,  less  oxygen  is  introduced 
into  the  kmgs,  to  consume  our  food- fuel. 

1159. 

Q.  Why  does  hard  work  produce  hunger  ? 
A.  Because  it  produces  quicker  rcspira- 


HUNGER. 


313 


hon;  by  which  means,  a  larger  amount  of 
oxygen  is  introduced  into  the  lungs^  and  tho 
capillary  combustion  increased.  Hunger  is  the 
no  ice  (given  by  our  body)  to  remind  us 
t\<it  our'  food-fuel  must  he  replenished. 

1160. 

Q.  Why  have  persons  who  follow  hardy 
out-of-doors  occupations  more  appetite  than 
those  who  are  engaged  in  sedentary  pur- 
suits ? 

A.  Hard  bodily  labor  in  the  open  air 
causes  much  oxygen  to  be  conveyed  into  the 
lungs  hy  inspiration ;  the  combustion  of  the 
food  is  carried  on  quickly ;  animal  heat  in- 
creased ;  and  need  for  nutritious  food  more 
quickly  indicated  by  craving  hunger. 

1161. 

Q.  Why  have  persons  who  follow  seden- 
tary  pursuits  less  appetite  than  ploughmen 
and  masons? 

A.  1st. — Because  the  air  they  inhale  is 
less  pure,  being  deprived  of  some  of  its  oxy- 
gen :  and 

2nd. — Their  respiration  is  neither  so 
quick  J  nor  so  strong;  and,  therefore,  the  com- 
bustion of  their  food  is  carried  on  more 
slowly. 

27 


3H 


ANIMAL  HEAT. 


1162. 

Q.  Why  do  persons  feel  lazy  and  averse 
to  exercise  when  they  are  half-starved  or 
ill'-fed? 

A.  Animal  food  contains  great  nourish' 
iiient,  and  produces  a  desire  for  active  occh 
pat  ions ;  but,  when  the  body  is  not  su}> 
pHed  with  strong  food,  this  desire  for  mus- 
cular action  ceases,  and  the  person  grow/? 
slothful. 

1163. 

Q.  Why  does  singing  make  us  hungry? 

A.  Because  it  increases  respiration;  and, 
as  more  oxygen  is  introduced  into  the  lungs. 
our  food-fuel  is  more  rapidly  consumed. 

1164. 

Q.  Why  are  the  ill-fed  mstinctively  averse 
to  cleanliness? 

A.  Because  cleanliness  increases  hunger^ 
which  they  cannot  allay  by  food. 

1165. 

Q.  Why  does  a  man  shrink  when  starved? 

A.  Because  the  capillary  fires  feed  upon 
the  human  body;  wheli  they  are  not  sup- 
plied with  food-fuel.  A  starved  man 
shrinks,  just  as  a  fire  does,  when  it  is  not  siip- 
plied  ^vith  fuel. 


SLEEP 


315 


1166. 

Q.  When  a  man  is  starved  what  parts  of 
the  body  go  first  ? 

A.  First  the  fat,  because  it  is  the  most 
combustible ;  then  the  muscles  ;  last  of  all 
the  brain;  and  then  the  man  dies,  like  a 
tandle  luhich  is  burnt  out. 

1167. 

Q.  Why  does  want  of  sufficient  nourish- 
ment often  produce  madness? 

A.  Because  after  the  fat  and  muscles  of 
the  body  have  been  consumed  by  animal 
combustion,  the  brain  is  next  attacked;  and 
(unless  the  patient  dies)  madness  ensues. 


CHAP,  v.— SLEEP. 

1168. 

Q  What  is  sleep  ? 

A.  Sleep  is  the  rest  of  the  brain  and  ner- 
vous  system. 

1169. 

Q.  Why  have  dreamers  no  power  of  judg- 
ment or  reason  ? 

A.  Because  the  ^^cerebrum^^  (oi  front  of 
the  brain)  is  inactive  and  at  rest. 

1170. 

Q.  Why  can  we  not  seey  when  we  are 
asleep  with  our  eyes  open  ? 


316  SLEEP. 

A.  Because  the  ''retina  of  the  eye'^  is 
inactive  and  at  rest. 

A  1171. 

Q.  Why  can  we  not  hear  in  sleep  ? 
A.  Because  the  nerve  of  hearing  (seatoil 
within  the  tympanum  of  the  ear)  is  at  rest. 

1172. 

Q.  Why  can  we  not  feel  when  we  ar(i 
nmeep  ? 

A.  Because  the  ends  of  the  nerves  (called 
papillse)  situated  in  the  skin,  are  inactive 
and  at  rest. 

1173, 

Q.  Why  can  wo  not  taste  when  we  are 
adeep  ? 

A.  Because  the  nerves  at  the  end  of  the 
tongue  (called  papillae)  are  inactive  and  at 
rest. 

1174. 

Q.  Why  have  persons  in  sleep  no  will  of 
<heir  own,  but  may  be  moved  at  the  will 
of  any  one  ? 

A.  Because  the  '' cerebellum^^  (or  pos- 
irrior  part  of  the  brain)  is  inactive  and  at 
r:.st. 

1175. 

Q.  Why  does  a  person  feel  when  he  is 
touched  1 


SLEEP. 


317 


A.  Because  the  ends  of  certain  nerves 
(ijalled  ''papillcE^')  situated  in  the  skin,  are 
excited;  and  produce  a  nervous  sensation 
called  feeling. 

1176. 

Q.  Why  do  some  persons  lose  all  power 
of  sensation? 

A.  Because  the  ^'cerebrum^^  (or  front  of 
their  brain)  has  been  injured. 

Q.  Why  are  persons  able  to  taste  differ- 
ent flavors? 

A.  Because  the  ^'papillcE^^  of  the  tongue 
and  palate  are  excited  when  food  touches 
them,  and  produce  a  nervous  sensation 
called  taste. 

1178. 

Q.  Why  is  a  dead  man  taller  than  a  liv- 
ing one  ? 

A.  Because  at  death  the  cartilages  are  re- 
laxed. So,  also,  after  a  night's  rest,  a  man 
is  taller  than  when  he  went  to  bed. 


CHAP.  VI.— ACIDS. 

1179. 

Q.  Why  does  pyroligneous  acid  prestrvt 
mmty  and  remove  its  taint  ? 

(Pyroligneous  acid,  is  vinegar  extracted  from  wood.) 


318 


ACIDS 


A.  Because  it  contains  a  small  quantit}? 
of  creasote,  which  is  a  great  preservative 
of  all  animal  substances. 

Creasote  from  the  Greek  words  xpcaT  creas  (flesh,)  and  cM^oi  solo  (1 
save,)  an  extract  from  the  oil  of  tar,  and  a  powerful  antisepiic. 

1180 

Q  Why  are  unripe  apples  and  goosebeV'- 
ries  sour? 

A.  Because  they  contain  rnalic  acid. 

Malic  from  the  Latin  word  malum,  an  apple. 
1181. 

Q.  Why  does  tanning  hides  convert  them 
into  leather  ? 

A.  Because  oak  bark  contains  tannic  acid; 
and  on  evaporation^  this  acid  precipitates  a 
solution  of  glue  upon  the  hides,  which  con- 
verts them  into  leather. 

1182. 

Q.  Why  do  old  wine  casks  smell  offensively? 

A.  Because  wine  (and  whiskey)  contain 
an  acid  called  oenanthic  acid  ;  which  unites 
with  the  alcohol  of  the  wine,  and  forms  a 
salt  of  an  offensive  smell. 

This  salt  is  called  the  cenanlhate  of  elhyle,  that  is,  the  winey  acid  oi 
ether. 

(Enanthate,"  from  the  Greek  word  (oivoT)  wine  ;  and  ethyle,'»  flora 
We  two  Greek  words  (aiOrjp-vXrj^  aither-ule)  the  basis  or  fundamental  prin- 
ciple of  ether. 

1183. 

Q.  Why  are  limes,  lemons,  and  mript 
vranges  sour  ? 


ACIDS. 


A.  Because  they  contain  citric  acid. 

Citric,  from  the  Latin  word  citrus,  a  lemon  or  citron^ 
1184. 

Q.  Why  are  tamarinds  and  unripe  grapes 
hour  1 

A.  Because  they  contain  tartaric  acid. 

Tartaric  acid  is  the  acid  of  tartar.  Tartar  is  a  substance  deposited  by 
whie  j  adhering,  like  a  hard  crust  to  the  sides  of  the  casks. 

1185. 

Q.  Why  does  rennet  curdle  milk  ^ 

A.  Because  it  converts  the  sugar  of  milk 

into  lactic  acid,  which  mixes  with  the  casein 

and  coagulates  it. 

Rennet  is  the  prepared  inner  membrane  of  the  stomach  of  a  calf;  and  if 
BO  called  from  the  German  word  rinnen  (to  curdle.) 

1186. 

Q.  Why  does  sour  milk  curdle  ? 

A.  Milk  consists  of  five  ingredients :  1, 
casein,  or  curd;  2,  butter ;  3,  sugar;  4,  wa- 
ter;  5,  certain  salts. 

The  casein,  or  curd  of  sweet  milk  is  like 
the  white  of  an  egg  before  it  is  boiled ;  but 
the  casein,  or  curd  of  sour  milk  is  like  the 
white  of  an  egg  after  it  is  boiled. 

This  casein,  or  curd  of  milk,  is  coagulated 
by  acids.  When  milk  is  sour  the  lactic  acid 
of  the  sour  milk,  mixing  with  the  casein, 
coagidates  it;  in  consequence  of  which,  it 
separates  from  the  water,  and  becomes  an 


320 


OILS. 


insoluble  mass;  or,  in  other  words,  the  milk 
curdles. 

*' Lactio  ;id/'  (from  the  Latin  word  Lac,  milk)  is  the  acid  of  sour 
milk.  Bvt  it  is  found  in  several  other  substances  also,  as  in  t.be  fermented 
fnice  of  '•^eel-root,  turnips,  carrots,  rice-water,  tanning-bark,  etc. 

1187. 

Q.  Why  is  vinegar  sour  ? 

A.  Because  it  contains  acetic  acid. 

Acetic*,  from  the  Saxon  word  (reced,)  vinegar;  whence,  ateo,  our  word 
itzid;  thi»t  is,  like  vinegar. 

1188. 

Q  If  wine  or  beer  be  imperfectly  corked, 
why  does  it  rapidly  turn  sour  ? 

A.  Because  air  gets  into  the  liquor  ;  and 
the  oxygen  of  the  air,  combining  with  the 
alcohol  of  the  liquor,  produces  acetic  acid, 
(or  vinegar.) 


CHAP.  VII.— OILS 

1189. 

Q.  Of  what  is  soap  made  ? 
A.  Of  kelp  (or  the  ashes  of  sea-weed  dried 
and  burnt  in  a  pit)  mixed  with  oil  or  fat. 

Yellow  soap  is  made  of  whale  oil,  soda,  and  resin.  Soft  soap  is  made 
of  o  l  and  potash.   Hard  soap,  of  oil  and  soda. 

1190. 

Q.  Why  does  soap,  when  laid  on  paint, 
destroy  it? 

A.  Because  the  soda  or  potash  of  which 
the  soap  is  composed,  destroys  or  jieutral 


OILS.  321 

izes  the  oil  in  the  paint,  and  sets  the  color- 
ing matter  free. 

1191. 

Q.  Why  does  soapy  water  "lather?'^ 
A.  Because  soap  makes  the  water  tena'^ 
cious,  and  prevents  its  bubbles  of  air  from 
bursting.      Lather is  only  an  accumula- 
tion  of  air  bubbles. 

Any  subs-tance  is  said  to  be  tenacious,  which  holds  fast  OT  retains  anoXhet 
-  thus  the  soapy  water  holds  or  retains  the  air-bubbles. 

1192. 

Q.  Why  is  it  impossible  to  wrice  on 
greasy  paper? 

A.  Because  grease  has  no  affinity  for  wa- 
ter or  ink,  and,  therefore,  will  not  mix  with 
it. 

1193. 

Q.  Why  does  turpentine  take  out  grease- 
spots  from  cloth  ? 

A.  Because  turpentine  dissolves  fixed  oils. 

The  Jixed  oils  are  all  greasy  oils,  such  as  sperm  oil,  olive  oil,  etc.  The 
other  sort  of  oils  called  volatile^  or  essential  oils,  are  those  used  in  per* 
fumery,  etc. 

1194. 

Q.  Why  is  mutton  fat,  etc.,  solid,  and  not 
liquid  ? 

A.  Because  fat  contains  a  predominance 
of  solid  stearine;  and  only  a  very  small 
quantity  of  the  liquid  oily  substance  called 
oktne.    On  the  other  hand,  oil  contains  more 


322 


OILS. 


of  tlie  liquid  oleine,  and  less  of  the  solid  mat 
ter  called  stearine. 

1195. 

Q  Why  is  butter  hard  in  cold  weather  ^ 
and  soft  in  warm? 

A.  Because  in  winter  the  weather  is  too 
cold  to  melt  the  stearine,  and  the  butter  is 
solid  ;  but  the  heat  of  summer  dissolves  it, 
or  holds  it  in  solution  in  the  oily  substance 
called  oleine,  and  the  butter  is  soft  and 
liquid. 

1196. 

Q.  Why  does  oil  become  thick  in  winter 
time? 

A.  1st. — Because  it  is  condensed  by  the 
cold,  and  rendered  more  solid ;  and 

2nd. — Because  the  '^stearine/'  which  is 
held  in  solution  in  warm  weather,  is  sepa- 
rated by  the  action  of  the  cold,  and  de- 
posited as  a  thick  white  and  almost  solid 
substance. 

"Stearine,"  (from  the  Greek  word  Trsap  [stear]  sutt,)  is  the  solid  o\ 
ftari  ingredienl  of  all  fat,  suet,  oil,  etc.  The  soft  or  liquid  pait  caLed 
oleine,  fronn  the  Latin  word  oleum^  (oil.) 

1197. 

Q.  What  is  the  difference  in  composition 
between  hard  and  soft  soap? 

A.  Hard  soap  is  made  of  soda,  and  sofl 
Roap  is  made  of  potash. 


OILS. 


323 


1198. 

Q  Soap  is  made  of  oil  or  fat.  How  is  it 
I  hat  oil  and  fat  make  water  greasy,  where- 
as, soap  destroys  grease  ? 

A.  Oil  contains  two  parts :  the  solid  part 
called  stearine^  and  the  liquid  part  called 
oleine. 

Stearine  of  oil  is  not  soluble  in  water;  but 
when  soda  or  potash  is  mixed  with  it,  the 
oily  principle  flies  off,  and  the  stearine  is 
converted  into  an  oxide  of  potassium,  which 
is  quite  soluble  in  water. 

Stearine,  from  the  Greek  word  Trsap  stear,  ^suet ;)  the  acid  of  stearine 
unites  with  the  soda  or  potash,  and  the  oily  prmciple  called  glycerine  fliea 
off. 

Oxide  of  potassium  is  the  fundamental  part  of  potash ;  it  i3  what  che- 
ir.isls  call  a  metallic  oxide. 

1199. 

Q.  From  what  is  salad  oil  made  ? 

A.  It  is  expressed  from  the  fruit  of  the 
olive  tree.  The  best  olive,  or  salad  oil,  is 
extracted  from  the  fruit  by  gentle  pressure 
in  the  cold. 

There  are  other  qualities  inferior  to  this, 
in  which  heat  aids  the  extraction  of  the  oil, 

1200. 

Q.  Why  does  churning  cream  convert  it 
into  butter? 

A.  Cream  is  the  fat  or  butter  of  milk  con- 
tained  in  little  globular  cases  of  albumen 


824  ANTIDOTES  FOR  POISONS. 


By  churning,  this  film  or  envelope  of 
albumen  is  broken,  and  the  butter  or  fat  set 
free. 

Tlie  globules  are  invisible  to  the  naked  eye,  but  may  be  distinctly  seen 
Sedating  about  milk,  by  means  of  a  tolerable  miscroscope. 

1201. 

Q   What  is  Indian-rubber  ? 

A.  Indian-rubber,  or  caoutchouc,  is  a 
vegetable  substance,  existing  in  the  milky 
juices  of  several  species  of  the  Jicus,  and 
oxidized  in  contact  with  the  air. 

"FicuSj"  the  fig  tribe  (a  species  of  fig  tree.) 
1202. 

Q.  What  is  guttapercha? 

A.  It  is  the  juice  of  a  tree  which  grows 
in  Malacca,  Borneo,  and  their  vicinities,  and 
becomes  oxidized  in  contact  with  the  air. 

Like  caoutchouc,  it  is  highly  elastic  when  heated  to  145^,  but  hardens 
again  when  cold.  It  is  so  tenacious,  that  a  piece  of  one-eighth  of  an  inch 
in  thickness,  when  cold,  will  suspend  one  hundred  and  forty  pounds  with- 
out breaking. 

The  botanical  name  is  doubtful,  by  some  it  is  said  to  be  the  Isonandra 
gutta. 


CHAP.  VIII.— ANTIDOTES  FOR  POISONS. 

1203. 

Q.  If  a  person  feels  faint  from  the  fumes 
of  prussic  acid,  what  is  the  best  antidote  ? 

A.  To  smell  the  vapors  of  strong  ammo- 
nia, {hartshorn,) 


ANTIDOTES  FOR  POISONS.  325 


1204. 

Q.  What  is  the  best  treatment  for  one 
who  has  swallowed  prussic  acid  ? 

A.  Apply  diluted  ammonia,  (hartshorn,) 
lo  the  nostrils,  and  let  a  stream  of  cold  w  a* 
ter  from  a  pitcher  fall  from  some  height  on 
the  region  of  the  spine. 

Electrical  shocks  are  said  to  be  very 
beneficial  also. 

1205. 

Q.  If  corrosive  sublimate  has  been  swallow- 
ed, what  is  the  best  antidote  ? 

A.  Albumen,  that  is,  the  white  of  an  egg — - 
the  yolk  of  the  egg  also  contains  albumen, 
together  with  an  oil,  which  is  a  good  anti- 
dote against  this  poison. 

Flour  and  water  mixed  to  the  consistence 
of  a  smooth  paste,  have  proved  efi&cacious. 

1206. 

Q.  If  an  over-dose  of  laudanum  has  been 
taken,  what  is  the  best  antidote  ? 

A.  Iodine,  three  grains ;  iodide  of  po- 
tassium, six  grains;  water,  one  pint; — to  be 
given  in  doses  of  a  wine-glassful. 

Vomiting  should  be  promoted  by  emetics. 

Electro-magnetism  is  often  efficacious  in 
restoring  the  nervous  sensibilities, 
28 


320  ANTIDOTES  FOR  POISONS.. 

1207. 

Q.  If  a  person  should  swallow  oxalic  ccid^ 
what  is  the  best  antidote  ? 

A.  Chalk  or  magnesia  mixed  with  a  little 
water. 

1208. 

Q.  What  is  the  best  antidote  to  verdigris? 
A.  Sugar,  or  the  white  of  egg. 

1209. 

Q.  If  chlorine  gas  has  been  taken,  im- 
moderately,  what  is  the  best  antidote  ? 

A.  Removal  to  a  current  of  fresh  air,  and 
the  inhalation  of  ammonia,  (hartshorn.) 

1210. 

Q.  Why  is  strong  green  tea  umoholesome  ? 
A.  Because  it  contains  prussic  acid,  which 
destroys  the  nervous  system. 

1211, 

Q.  Why  will  strong  Souchong  tea  poison 
flies? 

A*  Because  it  contains  prussic  acid^  which 
destroys  their  nervous  system. 


PART  V. 

METEOROLOGY. 


CHAP.  L— ATMOSPHERE. 

1212. 

Q.  What  is  meteorology  ? 

A..  It  is  a  science  which  has  for  its  ob- 
ject  the  investigation  of  the  changes  Avhich 
are  constantly  taking  place  in  the  atmo- 
sphere. The  knowledge  of  the  alterations 
of  the  weather,  and  the  laws  which  govern 
these  alterations,  is  styled  iveather-wisdom  or 
meteorology. 

1213. 

Q.  Of  what  is  atmospheric  «zr  composed? 

A.  Principally  of  two  gases,  oxygen  and 
nitrogen,  mixed  together  in  the  following 
proportion :  viz.,  1  gallon  of  oxygen  to  4 
of  nitrogen. 

It  mus*;  not  be  forgfotten  that  the  air  contains  small  quantities  of  Dti.ei 
Bfaseous  substances  also,  as  vapor  of  water,  carbonic  acid^  and  ammonict. 

1214. 

Q.  What  do  you  mean  by  a  gas  ? 
A.  An  elastic  fluid  resembling  air. 

N    IJ  Most  gases  are  invisible  or  colorless,  like  air, 

827 


328 


ATjIOSPIIERE. 


Elastic." — In  tnis  respect  gas  differs  from  a  liquid  which  is  AlmA«t 

int'lnstic  ;  whereas  gas  is  exceedingly  elastic. 

*'  Resembling  air."  or  aeriform.  The  word  Gas  "  means  atV,  bul 
itir  is  a  compound  of  two  gases.  Some  few  gases  are  visible,  as  ohlO' 
RTTPE,  which  is  a  greenish  yellow. 

1215. 

Q.  How  is  the  air  heated  ? 

A.  By  convection,  thus : — The  sun  heats 
the  earth,  and  the  earth  heats  the  air  resting 
upon  it ;  the  air  thus  heated  rises,  and  is 
succeeded  by  other  air,  which  is  heated  in  a 
similar  way ;  till  the  whole  volume  is 
warmed  by  ''convective  currents." 

1216. 

Q.  What  is  meant  by  "  convective  cur^^ 
rents     of  hot  air  ? 

A.  Streams  of  air  heated  by  the  earth, 
which  rise  upwards,  and  carry  heat  with 
them, 

1217. 

Q.  Does  the  sun  heat  the  air  as  it  does 
the  earth  ? 

A.  No ;  the  air  is  not  heated  by  the  rays 
of  the  sun;  because  air  (like  water)  is  a 
very  had  conductor. 

1218 

Q.  How  is  the  air  made  cold  ? 

A.  The  air  resting  on  the  earth  is  made 
wld  hy  contact ;  this  cold  air  makes  the  air 
ihove  it  cold  ;  and  cold  currents  (or  whids) 


ATMOSPHERE 


329 


shake  the  whole  together ^  till  all  becomes  of 
one  temperature. 

1219. 

Q.  How  is  the  air  made  fiot  or  cold? 
A .  By  convection  of  hot  or  cold  currents 

1220. 

Q.  Explain  this. 

A.  The  air  which  has  been  heated  by 
the  surface  of  the  earth  ascends,  warming 
the  air  through  which  it  passes.  Other 
air  (being  warmed  in  a  similar  way)  also 
ascends,  carrying  heat;  and  this  is  repeated 
till  all  the  air  is  made  hot. 

1221. 

Q.  What  effect  is  produced  upon  air  by 
coldl 

A.  It  is  condensed,  or  squeezed  into  a 
smaller  compass ;  in  consequence  of  which, 
it  becomes  heavier,  and  descends  towards  the 
ground. 

1222. 

Q.  Prove  that  air  is  condensed  by  cold. 

A.  Lay  a  bladder  half  full  of  air  before 
a  fire,  till  it  has  become  fully  inflated ;  if  it 
be  now  removed  from  the  fire,  the  bladder 
will  collapse  again,  because  the  air  con- 
donses  into  its  former  bulk. 
28* 


330 


ATMOSPHERE, 


1223. 

Q.  How  do  you  know  that  condensed  air 
will  descend  ? 

A.  Because  a  fire  balloon  falls  to  the 
earth,  so  soon  as  the  spirit  in  the  cotton  18 
burnt  out,  and  the  air  of  the  balloon  has  be 
€oine  cold  again. 

1224. 

Q.  What  is  meant  by  the  bladder  ^'coU 

Itipsing?^' 

A.  The  skin  becoming  wrinkled,  shri- 
velled,  and  flabby;  because  there  is  not  suffi- 
cient air  inside  to  fill  it. 

1225. 

Q.  Why  do  persons,  who  ascend  in  balloonSy 
feel  pain  in  their  eyes,  ears,  and  chest  ? 

A.  Because  the  air  in  the  upper  regions 
of  the  atmosphere  is  more  rare  than  the  air 
in  their  bodies ;  and  (till  equilibrium  is  re- 
stored) pain  will  be  fek  in  the  more  sensi- 
tive parts  of  the  body. 

More  especially  in  the  tympanum  of  the  ear. 
1226. 

Q.  Why  do  persons  wh  o  descend  in  divings 
bells,  feel  pain  in  their  eyes,  ears,  and  chest  I 

A.  Because  the  air  in  the  diving-bell  is 
compressed  by  the  upward  pressure  of  the 
water;   m  consequence  of  which,  great 


ATMOSPHERE. 


331 


pain  is  felt  in  the  more  sensitive  parts  of 
the  Ijody. 

The  pressure  thus  caused  is  sometimes  sufficient  to  ruptun  the  men)* 
brane  of  the  tympanum,  and  produce  incurable  deafness, 

1227. 

Q.  Why  do  we  feel  oppressed  just  pre 
vious  to  a  storm  ? 

A  Because  the  air  is  greatly  rarefied  by 
heat  and  vapor;  and  the  air  within  us  (seek- 
ing to  become  of  the  same  rarity)  produces 
an  oppressive  and  suffocating  feeling. 

1228. 

Q.  How  do  you  know  that  the  density 
of  the  air  is  lowered,  previous  to  a  storm  ? 

A.  Because  the  mercury  of  a  barometer 
rapidly  falls. 

1229. 

Q.  Why  do  cellars  feel  warm  in  winter  ? 

A.  Because  the  external  air  has  not  free 
access  into  them ;  in  consequence  of  which, 
they  remain  almost  at  an  even  temperature — 
which  (in  winter  time)  is  about  10"*  warmer 
than  the  external  air. 

1230. 

Q.  Why  do  cellars  feel  cold  in  summei  ? 

A.  Because  the  external  air  has  not  free 
access  into  them;  in  consequence  of  whicli, 
they  remain  aim  :)st  at  an  even  temper aturo — • 


332 


ATMOSPHERE. 


which  (in  summer  time)  is  about  10'*  colder 
than  the  external  air. 

1231. 

Q.  Why  is  it  often  painful  and  difficult 
to  breathe,  on  a  mountain-top? 

A.  Because  the  pressure  of  air  on  the 
mountain-top  ie.  not  so  great  as  it  is  on  the 
plain  ;  and  the  air  inside  our  bodies  (seek- 
ing to  become  of  the  same  rarity)  hursts 
through  the  pores  of  the  body  and  produces 
great  pain. 

1232. 

Q.  What  effect  has  heat  upon  the  air  ? 
A.  Heat  rarefies  the  air  and  causes  it  to 
expand. 

1233. 

Q.  How  do  you  know  that  heat  causes  the 
air  to  expand  ? 

A.  Thus,  if  a  bladder  half  full  of  air 
(tied  tight  round  the  neck)  be  laid  before  a 
fire,  the  air  will  expand  by  the  heat,  and 
fill  the  bladder. 

1234. 

Q.  What  is  a  barometer  ? 

A.  A  w^eather-glass,  or  instrument  to 
measure  the  variations  in  the  weight  of 
the  air ;  by  means  of  which  variations, 


ATMOSPHERE. 


333 


we  may  judge  what  weather  may  be  ex- 
pected. 

Barometer  is  a  compound  of  two  Greek  words  Tiapo'i  Baros  weigh:) 
and  [xsTpov  metroii  (a  measure.) 

1235. 

Q.  What  is  a  thermometer  ? 
A.  An  instrument  to  show  how  iot  or 
cold  anything  is. 

Tkkrmometer  is  a  compound  of  two  Geeek  words  OepfioT  thermoa 
(heat)  and  [icrpov  melron  (measure.) 

1236. 

Q  What  is  the  difference  between  a  ther- 
mometer  and  a  barometer  ? 

A.  In  a  thermometer  the  mercury  is  sealed 
up  from  the  air ;  and  rises  or  falls,  as  the 
varying  temperature  of  the  air  expands  or 
contracts  it ;  but 

In  a  barometer  the  mercury  is  left  exposed 
(or  open)  to  the  air^  at  its  lower  extremity, 
and  rises  or  falls,  as  the  varying  weight  of 
the  air  presses  upon  the  open  column. 

1237. 

Q.  If  the  mercury  of  the  thermometer  be 
sealed  up  from  the  air,  how  can  the  air  af- 
fect it  ? 

A.  The  heat  of  the  air  passes  through 
the  glass  tube  into  the  mercury,  which 
causes  the  metal  to  expand  and  rise  in  the 
tnbo. 


334 


ATMOSPHERE. 


1238. 

Q.  Why  is  the  tube  of  a  barometer  lefl 
vpen  ? 

A.  That  the  air  may  press  upon  it  freely ; 
jind,  as  this  pressm^e  varies,  the  mercury 
isi's  or  falls  in  the  tube. 

The  top  of  the  tube  must  be  a  vacuum  otherwise  the  pressure  of 
kfie  external  air  upon  the  lower  part  of  the  column  cannot  affect  the 
mercury. 

1239. 

Q.  How  can  a  barometer,  which  mea- 
sures the  weight  of  air,  be  of  service  as  a 
weather  glass  ? 

A.  When  air  is  moist,  or  filled  with  vapor, 
it  is  lighter  than  usual ;  and  the  column  of 
mercury  stands  low  ; 

When  air  is  dry  and  free  from  vapor,  it 
is  heavier  than  usual;  and  the  mercury 
stands  high .  Thus  the  barometer  (by  show- 
ing the  variations  in  the  weight  of  the  air) 
indicates  the  changes  of  the  weather  also. 

1240. 

Q.  The  height  of  mountains  may  be  ascer* 
tained  by  a  barometer;  explain  the  reason 
of  this? 

A.  As  we  ascend  a  high  mountain,  the 
quantity  of  air  above  us  becomes  less  and 
less  every  step  we  ascend,  and  requires  less 
mercury  to  balance  it ;  in  consequence  of 


ATMOSPHERE. 


335 


which,  the  mercury  in  the  tube  of  the 
barometer  falls. 

If  a  pile  of  books  be  placed  on  a  table,  the  bottom  book  will  sustain  the 
most  weight,  and  every  book  will  sustain  less  and  less,  as  we  get  nearer 
and  nearer  to  the  top ; — the  air  somewhat  resembles  this  pile.  That  cn 
the  surface  of  the  earth  resembles  ihe  bottom  book  of  the  pilej  and,  as  we 
ascend  a  mountain,  the  quantity  of  air  above  kreps  diminishing,  and  the 
weight  to  be  sustained  is  in  proportion  less 

For  general  purposes,  we  may  lake  this  for  a  lule,  for  every  one  hun- 
dred feet  of  perpendicular  height,  the  barometer  will  fall  one-tenth  of  an 
inch.  If,  therefore,  the  barometer  has  fallen  one  and  a  half  inch,  you 
know  the  mountain  is  fifteen  hundred  feet  higli. 

1241. 

Q.  Why  can  you  tell  (by  looking  at  a 
barometer)  what  kind  of  weather  it  will  be  ? 

A,  Because  the  mercury  in  the  tube  rises 
and  falls,  as  the  air  becomes  heavier  or 
lighter ;  and  we  can  generally  tell  by  the 
weight  of  the  air,  what  kind  of  weather  to 
expect. 

1242. 

Q.  What  use  is  a  barometer  to  sailors  ? 
A.  It  warns  them  to  regidate  their  ships, 
before  squalls  come  on. 

1243. 

Q.  How  can  a  barometer  warn  sailors  to 
regulate  their  ships? 

A.  As  it  indicates  when  wind,  rain,  and 
dorm  are  at  hand,  the  sailor  can  make  hia 
ship  trim  before  they  overtake  him. 


336 


WIND3> 


CHAP.  II.— WINDS. 

1244. 

Q.  What  is  wind? 

A.  Wind  is  air  in  motion. 

1245. 

Q  What  puts  the  air  in  motion,  so  as  to 
produce  wind? 

A.  The  principal  causes  are  the  valuations 
of  heat  and  cold,  produced  by  the  succession 
of  day  and  night,  and  of  the  four  seasons. 

1246. 

Q.  What  is  the  cause  of  wind  ? 

A.  The  sun  heats  the  earth,  and  the  earth 
heats  the  air  resting  upon  it ;  as  the  warm 
air  ascends,  the  void  is  filled  up  by  a  rush 
of  cold  air  to  the  place;  and  this  rush  of  air 
we  call  wind. 

1247. 

Q.  Does  the  wind  always  blow  ? 

A.  Yes ;  there  is  always  some  motion  in 
the  air ;  but  the  violence  of  the  motion  is 
perpetually  varying. 

1248. 

Q.  Does  the  rotation  of  the  earth  upon 
its  axis  effect  the  motion  of  the  air  ? 

A.  Yes,  in  two  ways.  1st. — As  the  earth 
moves  round  its  axis,  the  thin  moveable  air 
5^  left  somewhat  behind  :   and,  therefore, 


WINDS. 


337 


seems  (to  a  stationary  object)  to  be  blowing 
in  the  opposite  direction  to  the  eai  th's  mo- 
tion ;  and 

2nd. — As  the  earth  revolves,  different 
portions  of  its  surface  are  continually  pass- 
ing under  the  vertical  rays  of  the  sun. 

1249. 

Q.  When  are  the  rays  of  the  sim  called 
*^  vertical  raysV^ 

A.  When  the  sun  is  in  a  direct  line  above 
any  place,  his  rays  are  said  to  be  "vertical*^ 
to  that  place. 

1250. 

Q.  Illustrate  the  manner  in  which  the 
earth's  surface  passes  under  the  vertical  sub 

A.  Suppose  the  brass  meridian  of  a  globe 
to  represent  the  vertical  rays  of  the  sun ; 
as  you  turn  the  globe  round,  different  parts 
of  it  will  pass  under  the  brass  rim,  in  con- 
stant succession. 

1251. 

Q.  Why  is  it  noon-day  to  the  place  over 
which  the  sun  is  vertical  ? 

A.  Because  the  sun  is  half-way  between 
rising  and  setting  to  that  place. 

1252. 

Q.  Show  how  \h\s  rotation  i he  earth 
effects  the  rtir? 

29 


WINDS. 


A.  If  we  suppose  the  brass  meridian  to 
be  the  vertical  sun,  the  whole  column  of  air 
beneath  will  be  heated  by  the  noon-day  rayp; 
that  part  w^hich  the  sun  has  left,  will  be- 
come gradually  colder  and  colder ;  and  that 
part  to  which  the  sun  is  approaching^  will 
grow  constantly  warmer  and  loarmer. 

1253. 

Q.  Then  there  are  three  qualities  of  air 
about  this  spot  ? 

A.  Yes ;  the  air  over  the  place  which 
has  passed  the  meridian,  is  cooling;  the  air 
under  the  vertical  sun  is  the  hottest ;  and  the 
air  which  is  over  the  place  ahout  to  pass  un- 
der the  meridian,  is  increasing  in  heat. 

See  fi§r.  1.  The  column  A  (which  the  sun  has  passed)  is  cooling — B  is 
ander  the  vertical  sun ;  and  C  is  increasing  in  heat 

1254. 

Q.  Does  air  expand  by  heat  as  well  as 
water  ? 

A.  It  does ;  and  this  expansion  is  the 
eause  of  winds. 

1255. 

Q.  How  does  this  variety  in  the  heat  of 
air  produce  wind  ? 

A.  The  air  always  seeks  to  preserve  an 
equilibrium ;  so  cold  air  rushes  into  the  void 
made  by  the  upward  current  of  the  ivarm  air, 


839 


1256. 

Q.  Why  does  not  the  wuid  always  blow 
me  way,  following  the  direction  of  the  sun  1 

A.  Because  the  direction  of  the  wind  is 
gubject  to  perpetual  interruptions  from  hills ^ 
and  valleys^  deserts ^  seas,  etc. 

1257 

Q.  How  can  hills  and  mountains  alter  the 
course  of  the  wind  ? 

A.  Suppose  a  wind  (blowing  from  the 
north)  comes  to  a  mountain ;  as  it  cannot 
pass  through  it,  it  must  either  rush  hack  again, 
or  fly  off  at  one  side,  (as  a  marble,  when  it 
strikes  against  a  ivalL) 
125a 

Q.  Do  mountains  affect  the  wind  in  any 
other  way  ? 

A  Yes ;  many  mountains  are  capped  with 
snoio,  and  the  wartn  air  is  condensed,  when  it 
comes  in  contact  with  them ;  but  so  soon 
as  the  temperature  of  the  wind  is  changed,  its 
direc  t 'on  may  be  changed  also.  {See  Fig.  1  ) 

PIG   1.— THB  SUN. 


340 


WINDS. 


Suppose  A,  B,  C  to  be  three  columns  of  air.  A,  the  column  of  air  wriicn  u 
tooling  down  ;  B,  the  column  to  which  the  sun  is  vertical;  and  C,  the 
column  which  is  to  be  heated  next.  In  this  case  the  cold  air  of  A,  will  rush 
towards  B  C  ;  because  the  air  of  B  and  C  is  hotter  than  A.  But,  suppose 
now  C  to  be  a  snow-capped  mountain  :  As  the  hot  air  of  B  reaches  C,  it  ia 
chilled  ;  and  (being  now  colder  than  the  air  behind)  it  rushes  back  again 
towards  A,  instead  of  following  the  sun. 

1259. 

Q.  How  can  the  ocean  affect  the  direction 
of  the  wind  ? 

A.  When  the  ocean  rolls  beneath  the 
vertical  sun,  the  water  is  not  made  so  hot  as 
the  land;  in  consequence  of  which,  the  ge- 
neral direction  of  the  wind  is  directed  from 
tracts  of  ocean  towards  tracts  of  land. 

1260. 

Q.  Why  is  not  the  water  of  the  sea  made 
so  uot  by  the  vertical  sun,  as  the  surface  of 
the  land? 

A.  1st, — Because  the  evaporation  of  the 
sea  is  greater  than  that  of  the  land  ; 

2nd. — The  constant  motion  of  the  water 
prevents  the  increase  of  temperature  at  the 
surface ; 

3rd. — The  rays  of  the  sun  strike  into  the 
water ;  in  consequence  of  which,  the  im- 
mediate  surface  is  much  less  affected  ;  and 

4th. — Water  is  a  bad  conductor  of  heat. 

1261. 

Q.  Why  does  the  evaporation  of  the  sea 
prevent  its  surface  from  being  heated  by  the 
vertical  sun  ? 


WINDS. 


A.  Because  its  heat  is  uhsorhed  in  the  ge- 
neration of  vapor  and  carried  off  into  the  air 

1262. 

Q.  W[\y  does  the  motion  of  the  sea  pre- 
vent  its  surface  from  being  heated  by  the 
vertical  sun  ? 

A.  Because  each  portion  rolls  away,  as 
soon  as  it  becomes  heated,  and  is  succeeded 
bj  aiiotlur ;  and  this  constant  motion  pre- 
vents the  sur  face  of  the  sea  from  being  more 
heated  than  the  water  helovj  the  surface. 

1263. 

Q.  Why  are  those  winds,  which  blow 
over  large  continents,  or  tracts  of  land,  gene 
rally  dry  ? 

A.  Because,  in  their  passage,  they  absorb 
very  little  water,  as  they  do  not  blow  over 
large  oceans. 

1264. 

Q.  Why  do  our  hands  and  lips  chap  in 
frosty  and  windy  weather  ? 

A.  1st. — Because  the  wind  or  frost  ab- 
sorbs the  moisture  from  the  surface  of  the 
skin ;  and 

2nd. — The  action  of  wind  or  frost  pio- 
duces  a  kind  of  inflammation  on  the  skin. 

1265. 

Q.  Do  clouds  affect  the  ivind? 


S42 


WINDS. 


A.  Yes.  As  passing  clouds  screen  tlic 
direct  heat  of  the  sun  from  the  earth,  they 
diminish  the  rarefaction  of  the  air  also;  and 
this  is  another  cause  why  neither  the  strength 
iior  direction  of  the  wind  is  uniform. 

1266. 

Q.  Would  the  wind  blow  regularly  from 
east  to  west^  if  these  obstructions  were  re- 
moved 

A.  Without  doubt.  If  the  whole  earth 
were  covered  with  water,  the  winds  would 
always  follow  the  sun,  and  blow  uniformly 
in  one  direction. 

1267. 

Q.  Do  winds  ever  blow  regularly  ? 

A.  Yes;  in  those  parts  of  the  world 
which  present  a  large  surface  of  w^ater,  as 
in  the  Atlantic  and  Pacific  oceans. 

SECTION  I.  TRADE  WINDS. 

1268. 

Q.  What  are  the  winds  which  blow  over 
the  Atlantic  and  Pacific  oceans,  called  ? 
A.  They  are  called  "Trade  Winds.'' 

1269. 

Q  Why  are  they  called  ''Trade  Winds?'' 
A.  Because  they  are  very  convenient  to 
merchants,  who  have  to  cross  the  ocean. 


TRADE  WINDS. 


343 


iiuismuch  as  they  always  blo^v  in  one  di- 
rection. 

1270. 

Q.  In  what  direction  do  the  trade  winds 
blow  ? 

A  That  in  the  northern  hemisphere  blows 
from  the  north-east;  that  in  the  southern 
hemisphere  from  the  south-east. 

1271. 

Q.  Why  do  they  not  blow  from  the  full 
north  and  south  ? 

A  Because  currents  of  air  flowing  from 
the  poles ^  give  them  an  easterly  direction. 

This  effect  is  due  in  some  measure  to  the  rotation  of  the  earth  o'l  its 
1272. 

Q.  What  is  the  cause  of  these  currents  of 
air  from  the  poles  to  the  equator  ? 

A.  The  air  about  the  equator  constantly 
ascends,  in  consequence  of  being  rarefied  by 
the  heat  of  the  sun  ;  as  the  hot  equatorial 
air  ascends,  cold  air  from  the  north  and 
south  flows  towards  the  equator,  to  restore 
the  equilibrium. 

1273. 

Q.  Is  there  an  upper  as  well  as  a  lower 
current  in  the  atmosphere  ? 

A.  Yes ;  the  upper  current  of  rarefied  air 
is  from  the  equator  to  fie  poles ;  where  it  is 


341 


WLNTjS. 


conden»*5ed — and  then  returns  again  to  the 
equator,  forming  the  lower  current. 

1274. 

Q,  These  lower  currents  (from  the  poles  to 
I  he  equator)  have  an  ^(^^fcr/y  tendency.  Ex- 
plain the  cause  of  this  ? 

A  All  the  atmosphere  revolves  with  the 
mrth ;  but  when  a  current  of  air  from  the 
poles  flows  towards  the  equator,  it  comes  to 
a  part  of  the  earth's  surface  which  is  moving 
faster  than  itself in  consequence  of  which, 
it  is  left  behind,  and  thus  produces  the  effect 
of  a  current  moving  in  the  opposite  di- 
rection. 

Thus,  to  a  person  in  a  carriage,  the  hedges  and  trees  seem  to  be  running 
in  an  opposite  direction. 

As  the  circumference  of  the  earth  at  the  equator  is  much  larger  than  the 
circumference  of  ihe  earth  at  the  poles,  therefore,  every  spot  of  the  earth'g 
equatorial  surface  must  move  much  faster  than  the  corresponding  one  at 
the  poles. 

N.  B.  As  the  earth  revolves  on  its  axis  from  west  to  east,  therefore,  the 
Bir  which  is  carried  with  it  will  seem  to  blow  fro7n  the  weat  :  As,  how- 
ever, the  current  of  air  from  the  poles  seems  to  blow  in  the  opposite  di* 
rection,  it  will  seem  to  blow  from  the  east  (or  to  be  an  easterly  wind.) 

1275. 

Q.  By  what  means  are  the  north-east  and 
fiouth-east  trade  loinds  produced  ? 

A .  By  a  combination  of  the  two  moticms 
of  the  'polar  currents ;  which  produces  the 
hitermediate  directions  of  the  north-east  and 
wuth-east. 


TRADE  WINDS 


345 


1276. 

Q  Are  both  these  motions  of  the  polaf 
i^urrents  real  ? 

A.  No.  The  motion  from  the  east  to 
west  is  only  apparent.  As  the  earth  re- 
volves from  west  to  east^  the  air  carried  with 
it  will  be  a  west  wind ;  but  the  polar  cm^ 
rents  seem  to  h\ow  in  the  opposite  dirpxtion. 
merely  because  they  have  not  acquired  the 
same  velocity. 

1277. 

Q.  Do  trade  winds  blow  from  the  north- 
east and  south-east  a//  ih^  year  round? 

A.  Yes,  in  the  open  sea;  that  is,  in  the 
Atlantic  and  Pacific  Oceans,  for  about  SO"" 
each  side  of  the  equator. 

1278. 

Q.  What  do  the  north-easterly  and  south- 
easterly trade  winds  produce  when  they 
meet  near  the  equator  ? 

A.  A  region  of  calms  in  which  thick 
foggy  air  prevails,  with  sudden  showers  and 
thunder-storms. 

1279. 

Q.  Is  this  region  of  calms  ^x^c?  in  its  po- 
sition ? 

A.  No;  it  shifts  its  place  according*  to 
the  sun's  distance,  and  position  in  regard  to 


S46 


WINDS. 


the  equator  ;  being  sometimes  entirely  to  tlw 
north  of  the  equator,  and  occasionally  reach- 
ing as  far  as  2"*  south  of  it. 

1280. 

Q.  Do  the  trade  winds  blow  uniformly 
from  north-east  and  south-east  in  the  Indian 
Ocean? 

A.  No;  nor  yet  in  those  parts  of  the 
Atlantic  and  Pacific  which  verge  on  the  con- 
tinents. 

1281. 

Q.  How  do  the  trade  winds  in  the  Indian 
Ocean  blow  ? 

A.  From  April  to  October,  a  south-west 
wind  prevails ;  but  from  October  to  April, 
a  north-east. 

SECTION  11.  MONSOONS. 

1282. 

Q.  What  are  these  periodical  currents  of 
air  (which  affect  the  neighborhood  of  the 
Arabian,  Indian,  and  Chinese  Seas)  called 

A .  They  are  called  Monsoons. 

1283. 

Q.  How  far  do  the  limits  of  the  Monsoons 
extend  ? 

A.  They  extend  from  the  African  shore 
to  tjie  longitude  of  New  Guinea;  and  are 


MONSOONS. 


347 


felt  northward  as  far  as  the  parallel  of  lati 
tude,  which  crosses  the  Loochoo  Isles. 

The  Loochoo  Isles  are  about  24°  norlh  latitude,  and  130°  east  longitude. 
1284. 

Q.  Are  the  monsoons  as  powerful  as  tlie 
trade  winds  ? 

A.  They  are  far  more  so,  and  veiy  often 
amount  to  violent  gales. 

1285. 

Q.  Why  do  not  the  trade  winds  in  the 
Indian  Ocean  blow  south-west  from  April  to 
October? 

A.  Because  the  air  of  Arabia,  Persia,  In- 
dia, and  China,  is  so  rarefied  by  the  enor- 
mous heat  of  their  summer  sun,  that  the 
cold  air  from  the  south  rushes  towards  these 
countries,  across  the  equator,  (during  these 
six  months y)  and  produces  a  south-west  wind. 

1286 

Q.  To  what  distance  does  this  south-vjest 
wind  prevail? 

A.  From  3°  south  of  the  equator,  to  the 
shores  of  the  Arabian,  Indian,  and  Chinese 
Seas 

1287. 

Q.  Why  do  the  trade  winds  (in  the  hu 
dian  Ocean)  blow  north-east  from  October  to 
April  ? 

A.  Because  the  southern  part  oj  the  torrid 


348 


zone  is  most  heated,  when  the  sun  has  left 
the  northern  side  of  the  equator  for  the 
southern;  and  the  cold  air  from  the  north 
(rushing  towards  the  southern  tropic)  is  di- 
verted into  the  direction  of  north-east,  where 
it  continues  for  the  other  six  months  of  the 
}^ear 

1288. 

Q.  Why  are  the  monsoons  more  useful  to 
the  mariner  than  the  fixed  trade  winds? 

A.  Because  the  mariner  is  able  to  avail 
himself  of  these  periodic  changes,  to  go  in 
one  direction  during  one  half  of  the  year, 
and  to  return  in  the  opposite  direction  during 
the  other  half. 

1289, 

Q.  How  is  the  change  of  the  monsoons 
marked  ? 

A.  By  an  interval  of  alternating  calms 
and  storms. 

1290. 

Q.  Show  the  goodness  and  wisdom  of  God 
in  the  constant  tendency  of  air  to  equili- 
brium ? 

A.  If  the  torrid  zone  were  not  tempered 
by  cold  air  from  the  polar  regions,  it  would 
become  so  hot,  that  no  human  being  could 
.  endure  it.    If  (on  the  other  hand)  the  polar 
reo;ions  were  never  vv^'^rmed  by  hot  air  from 


MONSOONS. 


the  torrid  zone^  they  would  soon  become  in- 
sufferably cold. 

1291. 

Q  In  what  other  way  does  the  mingling 
of  the  polar  and  equatorial  atmosphere  act 
hnieficially  ? 

A.  In  the  equatorial  regions,  the  great 
abundance  of  vegetable  life  is  productive  of  a 
very  large  amount  of  oxygen;  in  the  colde'' 
regions,  artificial  fires  and  dense  masses  of 
animal  life,  produce  large  quantities  of  car- 
bonic acid.  The  mingling  of  the  polar  and 
equatorial  atmosphere  assists  in  supplying 
each  of  these  regions  with  the  very  gas  in 
which  it  would  be  otherwise  deficient. 

1292. 

Q.  Why  does  the  expansion  of  air  cause 
wind  ? 

A.  The  heat  of  the  sun  heats  that  part 
of  the  surface  of  the  earth  over  which  it  is 
vertical ;  the  heat  of  the  earth  thus  ac- 
quired by  absorption,  is  imparted  to  the 
lowest  stratum  of  air,  which,  becoming  ex- 
panded, rises  and  gives  place  to  another, 
and  in  this  manner  an  ascending  current  is 
established. 

The  colder  and  heavier  air  rushes  in  from 
the  colder  regions  north  and  south  to  fill 
30 


350 


WINDS. 


the  vacuum  tlius  occasioned,  thus  producing 
wind. 

"  Stratu7n^'^  layer.  The  lowest  stratum  of  air,  is  that  portion  of  an 
which  is  in  cuntact  with  the  surface  of  the  earth. 

1293. 

Q.  How  does  the  mingling  of  the  poker 
and  equatorial  atmosphere  serve  to  su]:)ply 
each  region  ^vith  the  gas  it  most  requires  ? 

A.  The  plants  of  the  equatorial  regions  re- 
quire carbonic  acid; — The  animals  of  the 
colder  regions  require  oxygen ; — The  cur- 
rents of  air  from  the  Poles  carry  carbonic  acid 
to  the  equatorial  plants ;  and  the  currents 
of  air  from  the  Equator  carry  oxygen  to  the 
animals  which  abound  nearer  the  Poles. 

1294. 

Q.  Why  does  vjind  dry  damp  linen  ? 

A.  Because  dry  wind  (like  a  dry  sponge) 
imbibes  the  particles  of  vapor  from  the  sur- 
face of  the  linen,  as  fast  as  they  are  formed. 

1295. 

Q.  Why  are  the  west  winds  in  the  At- 
lantic States  generally  dry  ? 

A.  Because  they  come  over  large  tracts  of 
land,  and  therefore,  absorb  very  little  water; 
and  being  thirsty,  they  readily  imbibe 
moisture  from  the  air  and  clouds,  and  there- 
fore bring  dry  weather. 

N.  B.  The  remarks  about  the  winds  in  this  work,  do  not  apply  to  thi 

*Vf;stern  Statee,  particularly  Texas  and  California, 


MONSOONS. 


351 


1296. 

Q.  Why  is  the  noiih  wind  generally  coM? 

A.  Because  it  comes  from  the  polar  re- 
gions,  over  mountains  of  snow  and  seas  of 
ice. 

1297. 

Q.  Why  are  north  winds  generally  drij? 

A.  Because  they  come  from  colder  re- 
p;ions,  and  being  warmed  by  the  heat  of  our 
climate,  absorb  moisture  from  every  thing 
they  touch;  in  consequence  of  which,  they 
are  generally  dry. 

1298. 

Q.  Why  are  south  winds  generally  warm? 

A.  Because  they  come  over  countries 
vv^armer  than  our  own,  where  they  are 
much  heated. 

1299. 

Q.  Why  are  winds  which  blow  over  a 
vast  body  of  water  generally  rainy? 

A.  Because  they  come  laden  with  vapor : 
if,  therefore,  they  meet  with  the  least  chul^ 
8ome  of  the  vapor  is  deposited  as  rain. 

1300. 

Q.  Why  is  the  rising  sun  in  summer, 
sometimes  accompanied  with  a  bi^eeze  ? 

A.  Because  the  heat  of  the  rising  sun 
stops  the  radiation  of  heat  from  the  earth, 
and  warms  its  surface. 


352 


WINDS. 


1301. 

Q.  How  does  this  warmth  produce  a 
breeze? 

A.  The  air  (resting  on  the  earth's  siir- 
iace)  being  warmed  by  contact  ascends^  and 
colder  air  rushing  in  to  fill  up  the  void,  pro- 
duces the  morning  breeze. 

1302. 

Q.  Why  is  there  often  an  evening  breeze 
during  the  summer  months  ? 

A.  Because  the  earth  radiates  heat  at  sun- 
set and  the  air  is  rapidly  cooled  down  by 
contact ;  this  condensation  causes  a  motion 
in  the  air,  called  the  evening  breeze. 

1303. 

Q.  Why  are  tropical  islands  subject  to  a 
sea  breeze  every  morning  ;  (that  is,  a  breeze 
blowing  from  the  sea  to  the  land  ?) 

A.  Because  solar  rays  are  unable  to  heat 
the  surface  of  the  sea,  as  they  do  the  earth; 
therefore,  the  air  resting  on  the  sea  is  less 
heated  than  the  air  resting  on  the  earth;  and 
the  colder  sea  air  blows  inland  to  restoie 
the  equilibrium. 

1304. 

Q.  Wliy  is  a  fine  clear  day  sometimes 
m^ercast  in  a  few  minutes  ? 

A.  Because  some  sudden  change  of  tev^ 


MONSOONS. 


353 


perature  has  condensed  the  vapor  of  the  air 
into  clouds. 

1305. 

Q.  Why  are  clouds  sometimes  dissipated 
vory  suddenly  ? 

A.  Because  some  dri/  loind  (blo^v^ing  over 
the  clouds)  imbibes  their  moisture,  and  carrier 
t  off  in  invisible  vapor. 

1306. 

Q.  Why  does  wind  sometimes  bring  rain 
and  sometimes  fine  weather  ? 

A.  If  the  wind  be  colder  than  the  clouds, 
it  will  condense  their  vapor  into  rain  ;  but 
if  the  wind  is  warmer  than  the  clouds,  it  will 
dissolve  them  and  cause  them  to  disappear 

1307. 

Q.  Why  is  a  land  breeze  unhealthy  ? 

A.  Because  it  is  frequently  laden  with 
exhalations  from  putrefying  animal  and  vege- 
table substances. 

1308. 

Q.  Why  is  a  sea  breeze  fresh  and  healthy? 
A.  Because  it  passes  over  the  sea,  and 
is  not  laden  with  noxious  exhalations. 

It  is  partieularlj'  healthy^  thereforp,  to  walk  on  the  sea-beach  before  ten 
7  clock  in  the  morning  ;  hut  unhealthy  after  sun- set 

1309 

Q.  What  is  the  cause  of  a  sea  breeze  ? 
A.  When  the  land  is  more  heated  by  (h^ 
30^ 


354 


WINDS. 


sun  than  the  sea  is,  the  land  air  becomes 
hotter  than  that  over  the  sea;  in  conse- 
quence of  which,  the  cooler  sea  air  glides 
inland  to  restore  the  equilibrium. 

1310. 

Q.  Why  does  a  sea  breeze  feel  cool  ? 

A.  Because  the  sun  cannot  make  the 
surface  of  the  sea  so  hot  as  the  land;  there- 
fore, the  air  which  blows  from  the  sea  is 
cooler  than  the  air  of  the  land. 

1311. 

Q.  Why  are  tropical  islands  subject  to  a 
land  breeze  every  evening,  (that  is  a  breeze 
blowing  from  the  land  towards  the  sea  ?) 

A.  Because  the  surface  of  the  land  cools 
down  faster  (after  sun-set)  than  the  surface 
of  the  sea:  in  consequence  of  which,  the 
air  of  the  cold  land  is  condensed — sinks  down 
— and  spreads  itself  into  the  warmer  sea 
air — causing  the  land  breeze. 

1312. 

Q.  Why  is  the  land  breeze  cool? 

A.  Because  the  surface  of  the  land  is 
cooled  at  sun-set  quicker  than  the  surface  of 
the  sea  ;  therefore,  seamen  feel  the  air  fi  f  uri 
the  land  to  be  chill. 

1313. 

Q  Explain  th  ^  cause  of  sea  leaves  ? 


MONSOONS. 


355 


A.  The  wind  (acting  on  the  suiface  of 
the  sea)  piles  up  ridges  of  water ^  leaving  be- 
hind an  indentation:  as  the  water  on  all 
sides  rushes  to  fill  up  this  indentation,  the 
disturbance  spreads  on  all  sides,  and  billow 
rolls  after  billow. 

1314 

Q.  Why  does  wind  generally  feel  cold  ? 

A.  Because  a  constantly  changing  surface 
comes  in  contact  with  our  body,  to  draw 
off  its  heat. 

1315. 

Q.  How  fast  does  wind  travel  ? 

A.  A  gentle  breeze  goes  at  about  the 
rate  of  five  miles  an  hour.  A  high  wind 
from  twenty  to  sixty.  A  hurricane  from 
eighty  to  one  hundred  miles  an  hour. 

1316. 

Q.  How  is  the  velocity  of  winds  ascer- 
tained ? 

A.  By  observing  the  velocity  of  the 
clouds ;  and  by  an  instrument  for  the  pur- 
pose, called  an  Anemometer. 

Pronounce  An-e-mom-'-e-ter.  From  two  Greelc  words  avsr^aT  ajiemoa 
(wind,)  and  i^erpov  metron  (a  measure.)  This  term  is  applied  more  fre- 
quently to  an  instrument  which  measures  the  force  of  wind. 

1317. 

Q.  How  is  the  velocity  of  the  clouds 
curtained  ? 


S56 


CLOUDS. 


A.  By  obsenang  the  speed  of  their  slia- 
(low  along  the  ground  ;  which  is  found  (in 
a  high  w^ind)  to  vary  from  twenty  to  sixty 
miles  an  hour. 


CHAP.  III.— CLOUDS. 

1318. 

Q  What  are  clouds  ? 

A.  Moisture  evaporated  from  the  earthy 
and  again  partially  condensed  in  the  upper 
regions  of  the  air. 

1319. 

Q.  What  is  the  difference  between  a  fog 
and  a  cloud  ? 

A.  Clouds  and  fogs  differ  only  in  one  re- 
fipect.  Clouds  are  elevated  above  our  heads : 
but  fogs  come  in  contact  with  the  surface  of 
the  earth. 

1320. 

Q.  Why  are  clouds  higher  on  a  fine  day? 
A.  Because  they  are  lighter  and  more 
b^ioi/ant. 

1321. 

Q.  Why  are  clouds  lighter  on  a  fine  day? 

A.  1st. — Because  the  vapor  of  the  clouds 
IS  less  condensed :  and 

2nd. — The  m  itself  (on  a  fine  day)  re- 
to  ins  much  ol  its  vapor  in  an  invisible  form 


CLOUDS.  35 

1322. 

Q.  Wliy  do  clouds  float  so  readily  in  the 
air? 

A.  Because  they  are  composed  of  Vhry 
minute  globules  (called  vesicles;)  which  (be- 
ing lighter  than  air)  float  like  soap  bubbles. 

1323. 

Q.  Are  all  clouds  alike  ? 
A.  No.    They  vary  greatly  in  density ^ 
height  J  and  color. 

1324. 

Q.  What  is  the  chief  cause  of  fog  and 
clouds  ? 

A.  The  changes  of  the  wind. 

Many  local  circumstances  also  favor  the  formation  of  clouds. 
1325. 

Q.  How  can  the  changes  of  the  wind  affect 
the  clouds  ? 

A.  If  a  cold  current  of  wind  blows  sud- 
denly over  any  region,  it  condenses  the  in- 
visible vapor  of  the  air  into  cloud  or  rain: 
but,  if  a  warm  current  of  wind  blows  over 
any  region,  it  disperses  the  clouds,  by  absorb* 
mg  their  vapor. 

132S. 

Q.  What  countries  are  the  most  cloudy  ? 
A.  Those  where  the  winds  are  most  vana* 
ble,  as  Great  Britain. 


358 


CLOUDS- 


1327. 

Q.  Wliat  countries  are  the  least  cloudy  ? 
A.  Those  where  the  winds  are  least  vw^ich 
hie  as  Egypt. 

1328. 

Q.  What  distance  are  the  clouds  from  the 
earth  ? 

A.  Some  tkin^  light  clouds  are  elevated 
above  the  highest  mountain- top;  some  heavy 
ones  touch  the  steeples,  trees,  and  even  the 
earth ;  but  the  average  height  is  between 
07ie  and  two  miles. 

N.  B.  Streaky,  curling  clouds,  like  hair,  are  often  five  or  six  milefl 
high. 

1329. 

Q.  What  clouds  are  the  lowest? 

A..  Those  which  are  the  most  highly  elec* 
trifled;  lightning  clouds  are  rarely  more 
than  about  seven  hundred  yards  above  the 
ground ;  and  often  actually  touch  the  earth 
with  one  of  their  edges. 

1339. 

Q.  What  is  the  size  of  the  clouds  ? 

A.  Some  clouds  are  tiomty  square  mdes  in 
surface,  and  above  a  mile  in  thickness;  while 
others  are  only  a  feia  yards  or  inches. 

1331 

Q.  How  can  persons  ascertain  the  thick* 
M.ess  of  a  cloud  ? 


CLOUDS. 


359 


A.  As  the  tops  of  high  mountains  are 
generally  above  the  clouds,  travellers  may 
pass  quite  through  them  into  a  clear  blue  fir- 
mament ;  when  the  clouds  will  be  seen  he- 
math  their  feet. 

1332. 

Q.  What  produces  the  great  variety  in  the 
shape  of  the  clouds  ? 

A.  Three  things:  1st. — The  cau^e  and 
manner  of  their  formation : 

2nd. — Their  electrical  condition  ;  and 

3rd. — Their  relations  to  currents  of  wind. 

■  333 

Q.  How  can  electricity  affect  the  shape  of 
*ilouds  ? 

A.  If  one  cloud  be  full  oj  ekctriaty  and 
another  not,  they  will  be  attracted  to  each 
other,  and  either  coalesce — diminish  m  size 
— or  vanish  altogether. 

1334. 

Q.  What  clouds  assume  the  most  fantastic 
tdiapes  ? 

A,  Those  that  are  the  most  hignly  electrt- 
fied. 

1335. 

Q.  What  effect  have  winds  on  the  shape 
of  clouds? 

A.  They  ?iome times  absorb  them  entirely 


3G0 


CLOUDS. 


sometimes  increase  their  volume  and  density  ^ 
and  sometimes  change  the  position  of  their 
parts. 

1336. 

Q.  How  can  winds  absorb  clouds  altogether? 

A  Warm,  dry  loinds  will  convert  the  sub- 
stance of  clouds  into  invisible  vapor,  which 
they  will  carry  away  in  their  own  current. 

1337. 

Q.  How  can  winds  increase  the  bulk  and 

density  of  clouds  ? 

A.  Cold  currents  of  wind  will  condense 
the  invisible  vapor  of  the  air,  and  add  it  to  the 
clouds  with  which  they  come  in  contact. 

1338. 

Q.  How  can  winds  change  the  shape  of 
clouds,  by  altering  the  position  of  their 
parts 

A.  Clouds  are  so  voluble  and  light,  that 
every  breath  of  wind  changes  the  position 
of  their  vesicles  or  bubbles. 

1339. 

Q.  What  are  the  general  colors  of  the 

(huds  ? 

A.  White  and  gray,  when  the  sun  is  above 
the  horizon  ;  but  red,  orange,  and  yellow,  at 
mn-rise  and  sun-set. 

The  blue  sJcy  is  not  cloud  at  all. 


CLOUDS. 


361 


1340. 


Q.  Why  are  the  last  clouds  of  evening 
generally  of  a  red  tinge  ? 

A.  Because  r^cZ  rays  (being  the  least  re- 
j  '-angible  of  all)  are  the  la^t  to  disappear. 


Suppose  P,  A,  to  be  the  red  rays ;  P,  B,  the  yellow ;  P,  C,  the  bhie.  If 
the  earth  turns  in  the  direction  of  P,  A,  D,  it  is  quite  manifest  that  a  spec* 
tator  will  see  A,  (the  red  rays,)  some  time  after  P,  C,  and  P,  B,  have  passed 
froir  sight. 


Q,  What  is  meant  by  being  ^^less  refran- 

gible  V 

A.  Being  less  able  to  be  bent.  Blue  and 
yellow  rays  are  more  easily  bent  below  the 
horizon  by  the  resistance  of  the  air ;  but  red 
rays  are  not  so  much  bent  down;  and,  there- 
fore, we  see  them  later  in  the  evening. 

As  at  A,  in  jRg.  2. 
1342. 

Q.  Why  are  morning  clouds  generally  of  a 
red  tinge  ? 


PIG.  2. 


1341. 


81 


362 


CLOUDS. 


A.  Because  red  rays  are  the  least  refran- 
gible of  all ;  and  not  being  hent  so  much  as 
blue  and  yellow  rays,  we  see  them  sooner 
of  a  morning. 

Thus  (figr.  2,)  if  the  earth  turned  in  the  direction  of  D,  A,  P,  a  specta^ 
fit  D,  would  see  A,  (the  red  rays)  long  before  he  saw  P,  B,  ard  P,  C 

1343. 

Q,  Why  is  not  the  color  of  clouds  always 
alike  ? 

A.  Because  their  size^  density ^  and  situa- 
tion^ in  regard  to  the  sun,  are  perpetually 
varying ;  so  that  sometimes  one  color  is  re- 
flected and  sometimes  another. 

1344. 

Q.  What  regulates  the  motion  of  the 
clouds? 

A.  Principally  the  2/;mc?5;  but  sometimes 
electricity  will  influence  their  motion  also. 

1345. 

Q.  How  do  you  know  that  clouds  move 
by  other  influences  besides  wind  ? 

A.  Because  (in  calm  weather)  we  often 
see  small  clouds  meeting  each  other  from  op- 
posite directions. 

1346. 

Q.  How  do  you  know  that  electricity  af. 
fects  the  motion  of  the  clouds  ? 

A.  Because  clouds  often  meet  from  oppo 
site  directions;  and,  having  discharged  their 


CLOUDS. 


363 


opposite  electricities  into  each  other,  vanuh 
altogether, 

1347. 

Q  What  are  the  uses  of  clouds  ? 

A.  1st. — They  act  as  screens,  to  arrest  th  < 
radiation  of  heat  from  the  earth  ; 

2nd. — They  temper  the  heat  of  the  sun\% 
rays  ;  and 

3rd. — They  are  the  great  store-houses  of 
rain. 

Radiation  of  heat,"  that  is,  the  escape  of  heat,  when  no  conductor 
carries  it  away. 

1348. 

Q.  Why  is  wind  said  to  blow  up  the  clouds? 

A.  Because  a  dry,  warm  wind  (which  has 
traveled  over  seas)  having  absorbed  a  large 
quantity  of  moisture,  deposits  some  of  it  in 
the  visible  form  of  clouds,  as  soon  as  it  reaches 
a  colder  region  of  air. 

1349. 

Q.  Why  does  wind  sometimes  drive  away 
the  clouds  ? 

A.  Because  it  has  traveled  over  dry 
dimes  or  thirsty  deserts,  and  become  so  dry, 
that  it  absorbs  vapor  from  the  clouds,  and 
causes  them  to  disappear. 

1350. 

Q.  What  is  the  cause  of  a  red  sun-set  ? 
A.   The  vapor  of  the  air,  not  being 


364 


CLOUDS. 


actually  condensed  into  clouds,  but  only  on  thu 
point  of  being  condensed. 

1351. 

Q.  Why  is  a  red  sun-set  an  indication  of 
a  fine  day  to-morrow  ? 

A.  Because  the  vapors  of  the  earth  aro 
not  condensed  into  clouds,  by  the  cold  of  sun- 
set. Our  Lord  referred  to  this  prognostic 
in  the  following*  words  :  When  it  is  even- 
ing ye  say  it  will  be  fair  weather,  for  the 
sky  is  red/'    (Matt.  xvi.  2.) 

1352. 

Q.  What  is  the  cause  of  a  coppery  yellow 
sun-set? 

A.  The  vapor  of  the  air  being  actually 
condensed  into  clouds. 

1353. 

Q.  Why  do  vapors  {not  actually  condensed) 
refract  red  rays,  while  condensed  vapor  re- 
fracts yellow  ? 

A.  Because  the  beams  of  light  meet  with 
very  little  resistance ;  in  consequence  of 
which,  those  rays  are  bent  down  to  the  eye, 
which  require  the  least  refraction,  such  as 
red. 

See  fig  2,  where  it  is  evident  that  the  red  ray,  P,  A,  is  less  bent  than  the 
yellow  ani  blue  rays,  P,  B,  P,  C. 

1354. 

Q  Why  do  condensed  vapors  refract  ycU 


CLOUDS. 


865 


ioiv  rajs,  whereas,  vapors  not  actually  con- 
densed refract  red  ? 

A.  Because  the  beams  of  light  meet  with 
ffiore  resistance  from  the  condensed  vapor ; 
in  consequence  of  which,  those  rays  are 
bent  down  to  the  eye,  which  are  more  re 
fr acted  than  the  red,  such  as  yellow. 

See  fig.  2,  where  it  is  evident,  that  the  yellow  ray,  P,  B,  is  more  ben 
than  the  red  ray,  P,  A. 

1355. 

Q.  Why  is  a  yellow  sun-set  an  indication 
of  wet  ? 

A.  Because  it  shows  that  the  vapors  of 
the  air  are  already  condensed  into  clouds;  rain, 
therefore,  may  be  shortly  expected. 

1356. 

Q.  What  is  the  cause  of  a  red  sun-rise  ? 
A.  Vapor  in  the  upper  region  of  the  air 
just  on  the  point  of  being  condensed. 

1357. 

Q.  Why  is  a  red  and  lowering  sky  at  sun- 
rise an  indication  of  a  wet  day  ? 

A.  Because  the  higher  regions  of  the  aii 
ore  laden  with  vapor  on  the  very  point  of 
condensation,  which  the  rising  sun  cannot 
disperse.  Hence  our  Lord's  observation, 
''In  the  morning  ye  say,  it  will  be  foul 
weather  to-day,  for  the  sky  is  red  and  low- 
ering."   (Matt.  xvT.  3.) 


366 


CLOUDS. 


1358. 

Q.  Why  is  a  graij  morning  an  indication 
of  a  fine  day  ? 

A.  Because  only  the  air  contiguous  to  the 
earth  is  damp  and  full  of  vapor.  There  are 
10  vapors  in  the  higher  regions  of  the  air, 
o  bend  down  to  the  eye  even  the  red  ray^ 
of  any  beam  of  light. 

1359. 

Q.  What  difference  (in  the  state  of  the 
air)  is  required,  to  make  a  gray  and  red  sun- 
rise 1 

A.  In  a  gray  sun-rise,  only  that  portion 
of  air  contiguous  to  the  earth  is  filled  with  va- 
por; all  the  rest  is  clear  and  dry.  But  in 
a  red  sun-rise  the  air  in  the  upper  regions  is 
so  full  of  vapor,  that  the  rising  sun  cannot 
disperse  it. 

1360. 

Q.  Why  is  a  gray  sun-set  an  indication  of 
wet? 

A.  Because  it  shows  that  the  air  on  the 
surface  of  the  earth  is  very  damp  at  sun-set ; 
which  is  a  plain  proof  that  the  air  is  satu- 
rated with  vapor;  in  consequence  of  which, 
wet  may  be  soon  expected  ;  hence  the  pro* 
verb — 

Evening  red  and  morning  gray, 
VVill  set  the  traveler  on  his  way ; 
But  evening  gray  and  morning  red, 
Will  bring  down  rain  upon  his  head  " 


CLOUDS, 


367 


1361. 

Q.  What  is  meant  by  an  aurora  borealis, 
or  northern  h'ght  ? 

A.  Luminous  clouds  in  the  north  of  the  ski/ 
at  night  time.  Sometimes  streaks  of  bluef 
purple,  green,  red,  etc,,  and  sometimes 
flashes  of  light,  are  seen. 

1362. 

Q.  What  is  the  cause  of  the  aurora  bo* 
realis^  or  northern  light  ? 

A.  Electricity  in  the  higher  regions  of  the 
atmosphere. 

1363. 

Q.  Why  does  a  haze  round  the  sun  indi- 
cate rain  ? 

A.  Because  the  haze  is  caused  by  very 
fine  rain  falling  in  the  upper  regions  of  the  air; 
when  this  is  the  case,  a  rain  of  five  or  six 
hours^  duration  may  be  expected. 

1364. 

Q.  Why  is  a  halo  round  the  moon  a  sure 
indication  of  rain? 

A.  Because  it  is  caused  by  fine  rain  fall- 
ing  in  the  upper  regions  of  the  air.  The 
larger  the  halo,  the  nearer  the  rain-clouds^ 
and  the  sooner  may  rain  be  expected. 

1365. 

Q.  Why  do  we  feel  almost  suffocated  in  a 
hot  cloudy  night  ? 


368 


CLOUDS. 


A  Because  the  heat  of  the  earth  cannot 
escape  into  the  upper  region  of  the  air  ;  hut 
is  pent  in  by  the  clouds,  and  confined  to  the 
surface  of  the  earth. 

1366. 

Q  Why  do  we  feel  sprightly  in  a  clear, 
bright  night  ? 

A.  Because  the  heat  of  the  earth  can 
readily  escape  into  the  upper  regions  of  the 
air,  and  is  not  confined  and  pent  in  hy  thick 
clouds. 

1367. 

Q.  Why  do  we  feel  depressed  in  spirits  on 
a  wety  murky  day? 

A.  1st. — Because  the  air  is  laden  with 
vapor,  and  has  (proportionally)  less  oxygen. 

2nd. — The  air  being  lighter  than  usual, 
does  not  balance  the  air  in  our  body  ;  and 

3rd. — Mr'ist  air  has  a  tendency  to  depress 
the  nervous  system. 

1368. 

Q.  What  is  meant  by  the  ^^air  balancing 
the  air  in  our  body 

A.  The  human  body  contains  air  of  a 
given  densit}^ ;  if,  therefore,  we  ascend  into 
"^arer  air,  or  descend  into  denser,  the  balance 
is  destroyed,  and  ive  feel  oppressed. 


MODIFICATION  OF  CLOUDS.  369 


1369 

Q.  Why  do  we  feel  oppressed,  if  the  air 
around  is  not  of  the  same  density  as  that  in 
our  body  ? 

A.  Because  if  the  air  be  more  dense  than 
our  body,  it  will  produce  a  feeling  of  op^ 
pression;  if  it  be  less  dense,  the  air  in  our 
body  will  produce  a  feeling  of  distension. 

SECTION  I.  MODIFICATION  OF  CLOUDS. 

1370. 

Q.  Into  how  many  classes  are  the  differ- 
ent sorts  of  clouds  generally  divided? 

A.  Into  three  classes  : — viz.  Simple,  In- 
termediate, and  Compound. 

1371. 

Q.  How  are  simple  clouds  sub-divided  ? 
A.  Into  1. — Cirrus;  2. — Cumulus;  and 
3. — Stratus  clouds. 

1372. 

Q.  What  sort  of  clouds  are  called  cirrus? 
A.  Clouds  like  fibres,  loose  hair,  or  thin 
streaks,  are  called  "  cirrus  clouds.'^ 

1373. 

Q.  Why  are  these  clouds  called  cirrus  ? 

A.  From  the  Latin  word  ciirus  a  lock 
of  hair,  or  curl.")  Cirrus  clouds  are  the 
most  elevated  of  all. 


•  870 


CLOUDS. 


1374. 

Q.  What  do  cirrus  clouds  portend? 

A.  When  the  streamers  point  upwards ^ 
the  clouds  are  fallings  and  rain  is  at  hand : 
hut  when  the  streamers  point  downwards, 
drought  may  be  expected. 

1375. 

Q.  What  sort  of  clouds  are  called  cum- 
ulus  ? 

A.  Cumulus  clouds  are  lumps,  like  great 
sugar-loaves — volumes  of  smoke — or  mountains 
hwering  over  mountains. 

1376. 

Q.  Why  are  these  monster  masses  called 
cumulus  clouds  ? 

A.  From  the  Latin  word  cumulus  ('^a 
mass  or  pile.'') 

1377. 

Q.  Wliat  do  cumulus  clouds  foreshow  ? 

A.  When  these  piles  of  cloud  are  fleecy^ 
and  sail  against  the  wind,  they  indicate  rain , 
but  when  their  outline  is  very  hard,  and 
they  come  up  with  the  wind,  they  foretell 
fine  weather. 

Cumulus  clouds  should  be  smaller  towards  evening  than  they  are  al 
noon.  If  they  increase  in  size  at  sun-set,  a  thunder-slorrr.  may  be  expected 
ill  the  night. 

1378. 

Q.  What  sort  of  clouds  are  called  stratus? 


MODIFICATION  OF  CLOUDS.  371 

A.  Creeping  mists,  especially  prevalent  in 
a  summer's  evening:  these  clouds  rise  at 
sun-set  in  low,  damp  places;  and  are  always 
nearer  the  earth  than  any  other  sort  of 
cloud. 

1379. 

Q.  Why  are  these  mists  called  stratus 
clouds  ? 

A.  Fiom  the  Latin  word  stratus  laid 
low,"  or  "  that  which  lies  low.") 

1380 

Q.  What  produces  cirrus  clouds? 

A.  Moisture  in  a  visible  form,  deposited 
in  the  higher  regions  of  the  atmosphere  by 
ascending  currents  of  heated  air. 

1381. 

Q.  What  produces  cumulus  clouds  ? 

A.  Masses  of  visible  vapor  passing  from 
the  places  where  they  were  formed,  to  other 
places  where  they  are  about  to  be  either 
lissolved,  or  deposited  as  falling  rain. 

1382. 

Q.  What  produces  stratus  clouds . 

A.  Beds  of  visible  moisture,  formed  by 
some  chilling  effects,  acting  along  the  di- 
'^ect  surface  of  thp  rarth. 


372  CLOUDS 

1383. 

Q.  How  are  the  intermediate  clouds  sub* 
divided  ? 

A.  Into  two  sorts.  1. — The  Cirro- Cu- 
mulus ;  and  2. — The  Cirro-Stratus. 

1384. 

Q  What  are  cirro-cumulus  clouds  ? 

A.  Cirro-cumulus  clouds  are  cirrus  clouds 
springing  from  a  massy  centre;  or  heavy 
masses,  edged  with  long  streaks  generally 
called    mares'  tails. 

A  system  of  small  round  clouds  may  be  called  cirro-cumulus. 
1385. 

Q.  What  do  cirro-cumulus  clouds  gene- 
rally forebode? 

A.  Continued  drought,  or  hot,  dry  wea« 
ther. 

1386. 

Q.  What  are  cirro-stratus  clouds  ? 

A.  They  compose  what  is  generally 
called  a  "mackerel  sky.''  This  class  of 
clouds  invariably  indicates  rain  and  wind ; 
hence  the  proverb — 

Mackerel's  scales  and  mares'  tails. 
Make  lofty  ships  to  carry  low  sails." 

1387. 

Q.  What  produces  cirro-cumulus  clouds  ? 
A.  Cumulus  clouds  dissolving  away  into 


MODIFICATION  OF  CLOUDS. 


373 


cirim  produce  the  intermediate  class,  called 
tf'rrO'Cumuhis. 

1388. 

Q  What  produces  cirro-stratus  clouds  ? 

A,  Cirrus  clouds  accumulating  into  demei 
UJ  asses  produce  the  intermediate  class,  called 
[iiro'Stratm. 

1389. 

Q.  How  are  compound  clouds  sub- divided? 

A.  Compound  clouds  are  also  subdivided 
into  two  sorts.  1. — The  Cumulo-Stratus; 
and  2. — The  Nimbus  clouds. 

1390. 

Q.  What  is  meant  by  cumulo-stratns 
clouds  ? 

A.  Those  clouds  which  assume  all  sorts 
of  gigantic  forms  ;  such  as  vast  towers  and 
rocks — huge  whales  and  dragons — scenes 
of  battle — and  cloudy  giants.  This  class 
of  clouds  is  the  most  romantic  and  strange 
of  all. 

1391. 

Q.  What  do  the  cumulo-stratus  clouds 
foretell? 

A.  A  change  of  weather  ;  either  from  fine 
to  rain,  or  from  rain  to  fine. 

1392. 

Q.  What  are  nimbus  clouds? 
32 


371 


CLOUDS. 


A.  All  clouds  from  which  rain  falls. — 
Nimbus  is  the  Latin  word  for  '^clouds  which 
bring  a  storm, 

1393. 

Q.  By  what  particular  character  may  the 
nimbus  (or  rain-cloud)  be  at  once  distin- 
giiished. 

A«  By  the  want  of  a  defined  outline  :  its 
edge  is  gradually  shaded  oflF  from  the  deep 
gray  mass  into  transparency, 

1394. 

Q.  What  appearance  takes  place  in  the 
clouds  at  the  approach  of  rain  ? 

A.  The  cumulus  cloud  becomes  stationary, 
and  cirrus  streaks  settle  upon  it,  forming  cu- 
mulo-stratus  clouds;  black  at  first,  but  after- 
wards of  a  gray  color. 

1395. 

Q.  Why  do  clouds  gather  round  mountain 
tops? 

A.  Because  the  air  (being  chilled  by  the 
cold  mountain  tops)  deposites  its  vapor 
there  in  a  visible  form  or  cloud. 

SECTION  II.  DEW. 

1396. 

Q.  What  is  dew? 

A.  Dew  is  the  vapor  of  the  air  cmdenscd 


DEW.  375 

by  coming  in  contact  with  bodies  colder 
than  itself. 

1397. 

Q.  Why  is  the  ground  sometimes  covered 
with  d^w? 

A.  Because  the  surface  of  the  earth  (at 
sun-set)  is  made  so  very  cold  by  radiation, 
that  the  warm  vapor  of  the  air  is  chilled  by 
contact  and  condensed  into  dew. 

1398 

Q.  What  is  the  difference  between  dew 
and  rain  ? 

A.  In  dew^  the  condensation  is  made  near 
the  earth's  surface. 

In  rain  the  drops  fall  from  a  considerable 
height. 

1399. 

Q.  What  is  the  cause  of  both  dew  and 
ram  ? 

A.  Cold  condensing  the  vapor  of  the  air 
when  near  the  point  of  saturation. 

1400. 

Q.  Why  do  mist  and  fog  vanish  at  sim* 
rise  ? 

A.  Because  the  condensed  particles  are 
again  changed  into  invisible  vapor  by  the 
heat  of  the  sun. 


376 


CLOUDS. 


1401. 

Q,  Why  is  the  earth  made  colder  than 
the  air  after  the  sun  has  set  ? 

A.  Because  the  earth  radiates  heat  very 
freely,  but  the  air  does  not;  in  consequence 
of  which,  the  earth  is  often  five  or  ten  de- 
grees colder  than  the  air,  (after  sun-set;) 
although  it  was  much  warmer  than  the  air 
during  the  whole  day. 

1402. 

Q.  Why  is  the  earth  warmer  than  the  air 
during  the  day. 

A.  Because  the  earth  absorbs  solar  heat 
very  freely,  but  the  air  does  not ;  in  conse- 
quence of  which,  it  is  often  many  degrees 
warmer  than  the  air,  during  the  day. 

1403. 

Q.  Why  is  the  surface  of  the  ground 
colder  in  a  fine  clear  night  than  in  a  cloud?/ 
one  ? 

A.  Because,  on  a  fine,  clear  star-light 
night,  heat  radiates  from  the  earth  freely,  and 
is  lost  in  open  space ;  but  on  a  dull  night, 
the  clouds  arrest  the  process  of  radiation. 

1404. 

Q.  Why  is  dew  deposited  only  on  a  fine, 
clear  night? 

A.  Because  the  surface  of  the  ground  ra^ 
Hates  heat  most  Ji  f^ehj  on  a  fine  night ;  and 


DEW. 


377 


(being  cooled  down  by  this  loss  of  heat) 
chills  the  vapor  of  the  air  into  dew. 

1405. 

Q.  Why  does  abundance  of  dew  in  the 
morning,  indicate  that  the  day  will  be  fine? 

A.  Because  dew  is  never  deposited  in 
Jnll  cloudy  weather,  but  only  in  very  clear 
calm  nights;  when  the  cold  currents  of  air 
are  not  mixed  with  those  of  a  warmer 
temperature. 

1406. 

Q.  Why  is  there  no  dew  on  a  dull,  cloudi/ 
night  ? 

A.  Because  the  clouds  arrest  the  radiation 
of  heat  from  the  earth;  and  (as  the  heat  can- 
not freely  escape)  the  surface  is  not  suffi- 
ciently cooled  down  to  chill  the  vapor  of  the 
air  into  dew. 

1407. 

Q.  Why  is  a  cloudy  night  warmer  than  a 
fine  one  ? 

A.  Because  the  clouds  prevent  the  radia- 
tion of  heat  from  the  earth  ;  in  consequence 
of  which  the  surface  of  the  earth  remains 
warmer. 

1408 

Q.  Why  is  dew  most  abundant  in  situa- 
tions most  exposed  ? 


378 


CLOUDS. 


A.  Because  the  radiation  of  heat  is  ni>t 
arrested  by  houses,  trees,  hedges,  or  any 
otlier  thin2f. 

1409. 

Q.  Why  is  there  scarcely  any  dew  under 
«  shadj^  tree  ? 

A.  1st. — Because  the  thick  foliage  of  a 
tree  arrests  the  radiation  of  heat  from  the 
earth:  and 

2nd. — A  leafy  tree  radiates  some  of  its 
own  heat  towards  the  earth;  in  consequence 
of  which,  the  ground  underneath  a  tree  is 
not  sufficiently  cooled  down  to  chill  the  va- 
por of  the  air  into  dew. 

1410. 

Q.  Why  is  there  never  much  dew  at  the 
^oot  of  walls  and  hedges  ? 

A.  1st. — Because  they  act  as  screens,  to 
arrest  the  radiation  of  heat  from  the  earth  ; 
and 

2nd. — They  themselves  radiate  some  por- 
tion of  heat  towards  the  earth ;  in  conse- 
quence of  which,  the  ground  at  the  foot  of 
walls  and  hedges  is  not  sufficiently  cooUd 
down,  to  chill  the  vapor  of  the  air  into 
dew. 

1411. 

Q.  Dud  very  rarely  flies  by  night.  Wliy 
•8  this  ? 


DEW. 


379 


A.  1st. — ^Because  the  dews  of  night 
moisten  the  dust  and  prevent  its  rising  into 
the  air :  and 

2nd. — As  the  surface  of  the  earth  is 
colder  than  the  air  after  sun-set,  the  cur- 
rent of  the  wind  will  incline  downward ; 
and  tend  rather  to  press  the  dust  down  than 
to  buoy  it  up. 

1412. 

Q.  Why  is  there  no  dew  after  a  windy 
night  ? 

A.  1st. — Because  the  wind  evaporates  the 
moisture,  as  fast  as  it  is  deposited ;  and 

2nd. — It  disturbs  the  radiation  of  heat ; 
and  thus  diminishes  the  deposition  of  dew 

1413. 

Q.  Why  are  volleys  and  hollows  often 
thickly  covered  with  dew,  although  they 
are  sheltered. 

A.  Because  the  surrounding  hills  pre- 
vent the  repose  of  air  from  being  disturbed; 
but  do  not  overhang  and  screen  the  valleys 
sufficiently  to  arrest  their  radiation. 

1414. 

Q.  Wliy  does  dew  fall  more  abundantly 
en  some  things  than  on  others  ? 

A.  Because  some  things  radiate  boat 


380 


CLOUDS. 


more  freely  than  others  ;  and,  therefore,  be- 
come much  cooler  in  the  night. 

1415. 

Q.  Why  are  things  which  radiate  heat 
most  freely  always  the  most  thickly  covered 
with  dewl 

A.  Because  the  vapor  of  the  air  is  chilled 
into  deio,  the  moment  it  comes  in  contact 
with  them. 

1416 

Q.  What  kind  of  things  radiate  heat  most 
freely  ? 

A.  Grass,  wood,  and  the  leaves  of  plants, 
radiate  heat  very  freely ;  but  polished 
metal,  smooth  stones,  and  w^oolen  cloth, 
part  with  their  heat  very  tardily. 

1417. 

Q.  Do  the  leaves  of  all  plants  radiate  heat 
equally  well  ? 

A.  No.  Rough,  woolly  leaves  (like  those 
of  a  holly-hock)  radiate  heat  much  more 
freely  than  the  hard,  smooth,  polished  leaves, 
of  a  common  laurel. 

1418 

Show  the  wisdom  of  God  in  making 
grass,  the  leaves  of  trees,  and  all  vegetables, 
excellent  radiators  of  heat  ? 

A.  As  vegetables  require  much  moisture, 
%xvSl  would  often  perish  without  a  plentiful 


DEW. 


381 


deposit  of  dew,  God  wisely  made  them  to 
radiate  heat  freely ,  so  as  to  chill  the  vapor 
(which  touches  them)  into  dew, 

1419. 

Q.  Will  polished  metals  smooth  stones,  and 
woolen  cloth,  readily  collect  dev.  ? 

A.  No.  While  grass  and  leaves  of  plants 
are  completely  drenched  with  dew  ;  a  piece  of 
polished  metals  or  of  woolen  cloth  (lying  on  the 
same  spot,)  will  be  almost  dry. 

1420. 

Q.  Why  -wonldi  polished  metal  and  woolen 
cloth  be  dry,  while  grass  and  leaves  are 
drenched  with  dew  ? 

A.  Because  the  polished  metal  and  woolen 
cloth  part  with  their  heat  so  slowly y  that  the 
vapor  of  the  air  is  not  chilled  into  dew  as  it 
passes  over  them. 

1421. 

Q.  Why  is  a  gravel  walk  almost  dry  when 
a  grass  plat  is  covered  thick  with  dew  ? 

A.  Because  grass  is  a  good  radiator,  and 
throws  off  its  heat  very  freely;  but  gravel  is 
a  very  had  radiator,  and  parts  with  its  heat 
very  slowly. 

1422. 

Q.  Is  that  the  reason  why  grass  is  satv 
rated  with  devj,  and  the  gravel  is  not  ? 


382 


CLOUDS. 


A.  Yes.  When  the  vapor  of  warm  air 
comes  in  contact  with  the  cold  grass,  it  is 
instantly  chilled  into  dew ;  but  it  is  not  so 
freely  condensed  as  it  passes  over  gravel,  be- 
cause gravel  is  not  so  cold  as  the  grass. 

1423. 

Q.  Why  does  dew  rarely  fall  upon  hard 
rocks  and  barren  lands  ? 

A.  Because  rocks  and  barren  lands  are 
so  compact  and  hard,  that  they  can  neither 
absorb  nor  radiate  much  heat ;  and  (as  their 
temperature  varies  but  very  little)  very  little 
dew  distils  upon  them. 

1424. 

Q.  Why  does  dew  fall  more  abundantly 
on  cultivated  soils  than  on  barren  lands  ? 

A.  Because  cultivated  soils  (being  loose 
and  porous)  very  freely  radiate  by  night  the 
heat  which  they  absorbed  by  day  ;  in  con- 
sequence of  which  they  are  much  cooled  down, 
and  plentifully  condense  the  vapor  of  the 
passing  air  into  dew. 

1425. 

Q.  Show  the  wisdom  of  God  in  this 
arrangement  ? 

A.  Every  plant  and  inch  of  land,  which 
needs  the  moisture  of  dew,  is  adapted  to  coU 


DEW. 


383 


led  it ;  but  not  a  single  drop  is  wasted  wheie 
its  refreshing  moisture  is  not  required. 

1426 

Q.  Show  the  wisdom  in  having  polished 
metal  and  woolen  cloth  bad  radiators  of  heat? 

A.  If  polished  metal  collected  dew  as 
easily  as  grass,  it  could  never  be  kept  dry  and 
free  from  rust.  Again,  if  woolen  garments 
collected  dew  as  readily  as  the  leaves  of 
trees,  we  should  be  often  soaking  wet,  and 
subject  to  constant  colds. 

1427. 

Q.  Show  how  this  affords  a  beautiful  illus- 
tration of  Gideon's  miracle,  recorded  in  the 
book  of  Judges,  vi.  37,  38? 

A.  The  fleece  of  wool  (which  is  a  very  bad 
radiator  of  heat)  was  soaking  wet  with  dew, 
when  the  grass  (which  is  a  most  excellent 
radiator)  was  quite  dry. 

1428. 

Q.  Was  this  not  contrary  to  the  laws  of 
nature  ? 

k.  Yes ;  and  was,  therefore,  a  plain  de-- 
^onstration  of  the  power  of  God,  who  could 
thus  change  the  very  nature  of  things  at  his 
will 

1429. 

Q.  Why  do  our  clothes  feel  damp  after  walk 
ing  in  a  fine  evening  in  spring  or  autumn  ? 


384 


CLOUDS. 


A.  Because  the  vapor  (condensed  by  the 
cold  earth)  lights  upon  them  like  dew. 

1430 

Q.  When  is  dew  most  copiously  distilled  ? 

A.  After  a  hot  day  in  summer  or  autumn, 
especially  if  the  wind  blow  over  a  body  of 
water. 

1431. 

Q.  Why  is  dew  distilled  most  copiously 
after  a  hot  day  ? 

A.  Because  the  surface  of  the  hot  earth 
radiates  heat  very  freely  at  sun-set,  and  (be- 
ing made  much  colder  than  the  air)  chills  the 
passing  vapor  and  condenses  it  into  dew. 

1432. 

Q.  Why  is  there  less  dew  when  the  wind 
blows  across  the  land;  than  when  it  blows 
over  a  body  of  water  ? 

A.  Because  the  winds  which  blow  across 
the  land  are  dry  and  arid  ;  but  those  which 
cross  the  water  are  moist  and  full  of  vapor. 

1433. 

Q.  How  does  the  dryness  of  the  wind  pre- 
vent dew-falls? 

A.  As  winds  which  blow  over  the  land 
are  very  dry,  they  imbibe  the  moisture 
of  the  ^lir ;  in  consequence  of  which,  there 
\8  very  little  left  to  be  condensed  into  dm. 


DEW. 


385 


1434. 

Q.  How  does  the  moisture  of  the  wind 
promote  dew-falls; 

A.  As  winds  which  blow  over  water  are 
rit mated  with  vapor,  they  require  very  little 
1  eduction  of  heat  to  cause  a  copious  deposition 
uj  dew. 

1435. 

Q.  Does  not  atr  radiate  heat,  as  well  as 
the  earth  and  its  various  plants  ? 

A.  No.  The  air  never  radiates  heat;  nor 
is  the  air  made  hot  by  the  rays  of  the  sun. 

1436. 

Q.  Why  is  evening  dew  injurious  to  health  ? 

A.  Because  it  is  always  laden  with  nox- 
ious exhalations  from  earth;  especially  in 
marshy  countries. 

1437. 

Q.  Is  honey 'dew  a  similar  thing  to  dew  1 
A.  No.  Honey-dew  is  a  sweet  liquid  shed 
by  a  very  small  insect  (called  the  aphis)  and 
deposited  in  autumn  on  the  under  surface 
of  favorite  leaves. 

1438. 

Q.  Does  honey-d.ew  injure  leaves,  or  do 
them  good  ? 

A.  It  injures  them  very  much,  by  filling 
^he  pores  with  a  thick,  clammy  liquid  ;  in 


386 


CLOUDS. 


consequence  of  which,  the  leaf  can  neither 
transpire  nor  absorb  its  needful  food. 

1439. 

Q.  What  effect  has  honey-dew  upon  tlie 
appearance  of  a  leaf? 

A.  After  a  little  time,  the  leaf  (being 
smothered  and  starved)  begins  to  turn  a  dingy 
yellow. 

1440. 

Q.  Are  not  ants  very  fond  df  honey-dew  ? 
A.  Yes ;  and  crawl  up  the  loftiest  trees 
in  order  to  obtain  it. 

1441. 

Q.  Why  is  a  dew-drop  round  ? 

A.  Because  every  part  of  it  is  equally  ba* 
lanced;  and,  therefore,  there  is  no  cause  why 
one  part  of  the  drop  should  be  further  from 
the  centre  than  another. 

1442. 

Q.  Why  is  the  dew-drop  (on  a  broad  leaf) 
sometimes  flattened? 

A.  Because  two  or  more  drops  of  dew  roll 
together,  and  make  one  large  spheroid  (or 
flattened  drop.) 

1443. 

Q.  Why  will  dew-drops  roll  ''bout  cabbage* 
plants,  poppies,  etc.,  without  wetting  the 
s^iu'face  ? 


DEW. 


387 


A.  Because  the  leaves  of  cabbages  and 
poppies  are  covered  with  a  very  fine  waxen 
powder ^  over  which  the  dew-drop  rolls  with- 
out wetting  the  surface,  as  a  drop  of  rain 
would  over  dust. 

1444. 

Q.  Why  does  not  a  drop  of  rain  wet  the 
dmt  over  which  it  rolls  ? 

A.  Because  dust  has  no  affinity  for  water, 
and,  therefore,  repels  it. 

144' 

Q.  Why  does  not  the  dew-drop  wet  the 
powder  of  the  cabbage-plant  ? 

A.  Because  the  fine  powder  which  covers 
the  cabbage  leaves  has  no  affinity  for  water, 
and,  therefore,  repels  it. 

1446. 

Q.  Why  will  dew-drops  roll  over  a  rose, 
etc.,  without  wetting  the  petals? 

A.  Because  the  leaves  of  a  rose  contain 
an  essential  oil,  which  has  no  affinity  for  wa* 
ter,  and,  therefore,  repels  it. 

M47. 

Q.  Why  can  swans  and  ducks  dive  under 
water  without  being  wetted  ? 

A.  Because  their  feathers  are  covered 
with  an  oily  secretion,  which  has  no  affinity 
for  water  and,  therefore,  repels  it. 


3P8 


CLOUDS. 


SECTION  III.  RAIN,  SNOW,  IIAIL. 

1448. 

Q.  Wliat  is  Rain  ? 

A.  Rain  is  the  vapor  of  the  clouds  or  air, 
condensed  and  precipitated  to  the  earth. 

1449. 

Q.  Does  rain-water  possess  any  fertilizing 
properties,  besides  that  of  mere  moisture  ? 

A.  Yes ;  rain-water  contains  an  abun- 
dance of  carbonic  acid,  and  a  small  quantity 
of  ammonia  ;  to  which  much  of  its  fertilizing 
power  may  be  attributed. 

Ammonia  is  a  compound  of  nitrogen  and  hydrogen.  Common  hartshorn 
is  only  ammonia  and  water. 

1450. 

Q.  Why  are  there  more  rainy  days  from 
September  to  March,  than  from  March  to 
September  ? 

A.  Because  the  temperature  of  the  air  is 
constantly  decreasing,  and  its  capacity  for 
holding  vapor  decreases  also ;  in  conse- 
quence of  which,  it  is  frequently  obliged  to 
part  with  some  of  its  vapor  in  rain. 

1451. 

Q.  In  what  part  of  the  world  does  rain 
fall  most  abundantly  ? 

A.  Near  the  equator  ;  and  the  quantity  of 
rain  decreases  as  we  approach  the  poles. 

Be  it  remembered,  that  there  are  fewer  rainy  days^  although  more  mm 
%ctunlly  falls  during  the  wet  season  of  the  equator,  than  falls  in  tueWe 
ffioi  ihs  at  a)»y  other  part  of  the  globe. 


RAIN,  SNOW  HAIL. 


389 


1452. 

Q.  Why  is  there  less  rain  frora  March  to 
SeptfMber,  than  from  September  to  March  ? 

A.  Because  the  temperature  of  the  air  is 
const aiitly  increasing;  on  which  account  its 
capacity  for  holding  vapor  is  on  the  increase 
end  very  little  is  precipitated  as  rain. 

1453. 

Q.  Why  does  rain  fall  in  drops? 

A.  Because  the  vapory  particles  in  theii 
descent  attract  each  other ;  and  those  which 
are  sufficiently  near  unites  and  form  into 
drops. 

1454. 

Q.  Why  does  not  the  cold  of  night  always 
cause  rain  ? 

A.  Because  the  air  is  not  always  near 
saturation ;  and  unless  this  be  the  case,  it 
will  be  able  to  hold  its  vapor  in  solution, 
even  after  it  is  condensed  by  the  chilly 
night. 

1455. 

Q.  Why  does  a  passing  cloud  often  drop 
rain  ? 

A.  Because  the  cloud  (traveling  about  on 
tlie  wind)  comes  into  contact  with  something 
that  chills  it;  and  its  vapor  being  condensed 
falls  to  the  earth  as  rain. 

33* 


390  CLOUDS 
1456. 

Q.  Why  are  rain-drops  sometimes  much 
larger  than  at  other  times  ? 

A.  Because  the  rain-cloud  is  floating  near 
the  earth ;  when  this  is  the  case  the  drops 
are  large,  because  such  a  cloud  is  much 
jiore  dense  than  one  more  elevated. 

The  size  of  the  rain-drop  is  also  increased  according  to  the  rapidity  with 
which  the  vapcrs  are  condensed. 

1457. 

Q.  Does  not  wind  sometimes  increase  the 
nze  of  rain-drops  ? 

A.  Yes ;  by  blowing  two  or  more  drops 
into  one. 

1458. 

Q.  Why  do  clonds  fall  in  rainy  weather  ? 

A.  1st. — Because  they  are  heavy  with 
abundant  vapor ;  and 

2nd. — The  density  of  the  air  being  di- 
minished ^  is  less  able  to  buoy  the  clouds  up. 

1459. 

Q.  How  do  you  know  that  the  density  of 
the  air  is  diminished  in  rainy  weather  ? 

A.  Because  the  mercury  of  a  barometer 
falls. 

1460. 

Q.  Why  is  min-water  more  fertiliziig  than 
pvmp'Vjater  ? 


RAIN,  SNOW,  HAIL. 


391 


A.  Isfc. — Because  it  contains  more  car- 
bonic acid ;  and 

2nd.-  -It  contains  also  a  small  quantity 
of  ammonia,  with  which  it  supplies  the 
young  plants. 

It  '.s  probable  that  the  ammonia  of  rain-water  i&  merely  that  whick 
asr^pes  from  putrefying  animal  matters,  beaten  back  by  the  force  of  th6 
shower. 

1461 

Q.  Why  does  rain  purify  the  air  ? 

A.  1st. — Because  it  heats  down  the  noxious 
exhalations  collected  in  the  air,  and  dissolves 
them ; 

2nd. — It  mixes  the  air  of  the  upper  re- 
gions with  that  of  the  lower  regions;  and 

3rd. — It  washes  the  earth,  and  sets  in  mo- 
tion the  stagnant  contents  of  sewers  and 
ditches. 

1462. 

Q.  Why  are  mountainous  countries  more 
rainy  than  flat  ones  ? 

A.  Because  the  air  (striking  against  the 
sides  of  the  mountains)  is  carried  up  the  in- 
clined plane,  and  brought  in  contact  with  the 
cold  air  of  the  higher  regions ;  in  conse- 
quence of  which,  its  vapor  is  condensed,  and 
deposited  in  rain. 

1463. 

Q.  Why  does  a  sponge  swell  when  it  is 
wetted  ? 


392 


CLOUDS. 


A.  Because  the  water  penetrates  the  poreh 
of  the  sponge  by  capillary  attraction,  and 
drives  the  particles  further  from  each  other  ; 
in  consequence  of  which,  the  hulk  of  the 
sponge  is  greatly  increased. 

1464. 

Q.  Why  do  fiddle-strings  snap  in  wet  wea- 
ther? 

A.  Because  the  moisture  of  the  air  (pene- 
trating the  string)  causes  it  to  swell;  and  (as 
the  cord  thickens)  its  tension  is  increased,  and 
the  string  snaps. 

1465 

Q.  Why  does  paper  pucker  when  it  is 
wetted? 

A.  Because  the  moisture  (penetrating  the 
paper)  drives  its  particles  further  apart ;  and 
(as  the  moisture  is  absorbed  unequally  by 
the  paper)  some  parts  are  more  enlarged 
than  others  ;  in  consequence  of  which,  the 
paper  blisters  or  puckers. 

1466. 

Q.  Why  do  candles  and  lamps  spirt,  when 
ram  is  at  hand  ? 

A.  Because  the  air  is  filled  with  vapor 
which  penetrates  the  wick;  where  (being 
fo)  med  into  steam)  it  expands  suddenl}',  nnd 
]U'-)dnces  a  little  explosion. 


RAIN,  SNOW,  HAIL. 


393 


1467. 

Q.  In  which  part  of  the  day  does  the  most 
rain  fall  ? 

A.  More  rain  falls  by  night  than  by  day; 
because  the  cold  night  condenses  the  air^  and 
diminishes  its  capacity  for  holding  vapor  m 
solution. 

1468. 

Q.  Does  more  rain  fall  in  summer  cr  m 
lointer? 

A.  There  are  more  rainy  days  from  Sep- 
tember to  March ;  but  heavier  rains  between 
March  and  September. 

1469. 

Q.  What  beneficial  effect  has  rain  upon 
fallen  leaves  ? 

A.  It  hastens  the  putrefaction  of  the  fallen 
leaves ;  and  this  makes  the  earth  fertile. 

1470. 

Q.  Why  do  swallows  fly  low,  when  rain 
is  at  hand  ? 

A.  Because  the  insects  (of  which  they  are 
in  pursuit)  have  fled  from  the  cold,  upper  re- 
*  onions  of  the  air,  to  the  warm  air  near  the 
earth ;  and,  as  their  food  is  low,  the  swal- 
lows fly  low. 

1471. 

Q  Why  do  these  insects  seek  the  lowei 


894 


CLOUDS. 


regions  of  the  air  in  wet  weather,  more  than 
in  fine  weather  ? 

A.  Because  (in  wet  weather)  the  upper 
regions   of  the   air  are  colder  than  th 
lower;  and,  as  insects  enjoy  warmth,  they 
seek  it  near  the  earth. 

1472. 

Q.  Why  do  sea-gulls  fly  about  the  sea  in 
fine  weather  ? 

A,  Because  they  live  upon  the  fishes,  which 
are  found  near  the  surface  of  the  sea  in  fine 
weather. 

1473. 

Q.  Why  may  we  expect  stormy  rains, 
when  sea-gulls  assemble  on  the  land  ? 

A.  Because  the  fishes  (on  which  they 
live)  leave  the  surface  of  the  sea  in  stormy 
weather,  and  are  beyond  the  reach  of  the 
sea-gulls;  in  consequence  of  which,  they  are 
obliged  to  feed  on  the  worms  and  larvce. 
which  are  driven  out  of  the  ground  at  such 
times. 

*^Larvx,^^  little  grubs  and  caterpillars 
14  74. 

Q.  Why  do  petrels  fly  to  the  sea  during  a  ^ 
Btorm  ? 

A.  Because  they  live  upon  sea  insects, 
which  are  always  to  be  found  in  abundance? 
abmit  the  spray  of  swelling  waves. 


RAIN,  SNOW,  HAIL.  395 

tH.  II.  Petrels  are  birds  of  the  duck-kind,  which  live  in  the  open  iea 
They  run  on  the  top  of  the  waves,  and  are  called  Petrels,  or  rather  Peter 
els,  from  "St.  Peier,"  in  allusion  to  his  walking  on  the  sea,  to  go 
fetuB. 

1475 

Q.  What  is  snow  ? 

A.  The  condensed  vapor  of  the  air  frozen 
and  precipitated  to  the  earth. 

1476. 

Q.  AVhat  is  the  cause  of  snow  ? 

A.  When  the  air  is  nearly  saturated  with 
vapor,  and  condensed  by  a  current  of  air 
below  freezing  point,  some  of  the  vapor  is 
condensed,  and  frozen  into  snow. 

A  few  years  ago,  some  fishermen  (who  wintered  at  Nova  Zembla,) 
after  ihey  had  been  shut  up  in  a  hut  for  several  days,  opened  the  window, 
and  the  cold  external  air  rushing  in,  instantly  condensed  the  air  of  the  hut, 
ind  its  vapor  fell  on  the  floor  in  a  shower  of  snow. 

1477. 

Q.  Why  does  snow  fall  in  winter  time  ? 

A.  Because  the  sun's  rays  are  too  oblique 
to  heat  the  surface  of  the  earth ;  and  (as 
the  earth  has  no  heat  to  radiate  into  the  air) 
the  air  is  very  cold. 

1478. 

Q  What  is  the  cause  of  sleet  ? 

A.  When  flakes  of  snow  (in  their  descent) 
pass  through  a  bed  of  air  above  freezing  point, 
they  partially  melt :  and  fall  to  the  earth  aa 
half  melted  snow,  or  sleet. 

1479 

Q.  What  is  the  use  of  snow? 


396 


CLOUDS. 


A.  To  keep  the  earth  warniy  and  tc 
nourish  it. 

1480. 

Q.  Does  snow  keep  the  earth  warm  ? 

A.  Yes,  because  it  is  a  very  had  cm- 
iudoi ;  in  consequence  of  which,  when  the 
earth  is  covered  with  snow,  its  temperature 
very  rarely  descends  below  freezing  point, 
even  when  the  air  is  fifteen  or  twenty  de- 
grees colder. 

1481. 

Q.  Why  is  snow  a  had  conductor  of  heat 
and  cold? 

A.  Because  air  is  confined  and  entangled 
among  the  crystals ;  and  air  is  a  very  had 
conductor :  when,  therefore,  the  earth  is 
covered  with  snow,  it  cannot  throw  off  its 
heat  by  radiation. 

1482. 

Q.  Tell  me  the  words  of  the  Psalmist 
(cxlvii.  16)  respecting  snow;  and  explain 
what  he  means  ? 

A.  The  Psalmist  says — "The  Lord  giv- 
eth  snow  like  wool;''  and  he  means,  not 
only  that  snow  is  as  white  as  wool,  but  that 
it  is  also  as  warm  as  wool. 

1483. 

Q.  Why  is  iiml  loarm? 


RAIN,  SNOW,  HAIL. 


397 


A.  Because  air  is  entangled  among  the 
fibres  of  the  wool ;  and  air  is  a  very  had 
rondvctor. 

1484. 

Q  Why  is  snow  warm  ? 

A.  Because  air  is  entangled  among  the 
crystals  of  the  snow ;  and  air  is  a  very  bod 
conductor. 

1485. 

Q.  Why  does  snow  nourish  the  earth? 

A.  Because  it  supplies  moisture  contain- 
ing carbonic  acid;  which  penetrates  slowly 
into  the  soil,  and  insinuates  itself  through 
every  clod,  ridge,  and  furrow. 

I486. 

Q.  Why  is  there  no  snow  in  summer  timel 
A.  Because  the  heat  oj  the  earth  melts  it 
in  its  descent,  and  prevents  it  from  reach- 
ing the  surface  of  the  earth 

1487. 

Q.  Why  are  some  mountains  always  covered 
with  snow  ? 

A.  1st. — Because  the  air  on  a  high 
mountain  is  more  rarefied  ;  and  rarefied  air 
retains  much  heat  in  a  latent  state  :  and 

2nd. — Mountain- tops  are  not  surrounhd 
by  earth,  to  radiate  heat  into  the  air;  and, 
therefore,  tlie  snow  is  not  melted  in  its  de- 
34 


SOS 


CLOUDS. 


ecent,  but  falls  on  the  mountain,  and  lieti 
there. 

1488. 

Q.  Why  is  snow  white  ? 

A.  Because  it  is  formed  of  an  infinite 
number  of  very  minute  crystals  and  prisms^ 
which  reflect  all  the  colors  of  the  rays  of 
light  from  different  points ;  and  these  co- 
lors, uniting  before  they  meet  the  eye,  cause 
snow  to  appear  white. 

The  same  answer  applies  to  salt,  loaf-sugar,  etc. 
1489. 

Q.  What  is  hail  1 

A.  Rain,  which  has  passed  in  its  descent 
through  some  cold  bed  of  air,  and  has  been 
frozen  into  drops  of  ice. 

1490. 

Q.  What  makes  one  bed  of  air  colder  than 
another  ? 

A.  It  is  frequently  caused  by  electricity 
unequally  distributed  in  the  air. 

1491. 

Q  Why  is  hail  frequently  accompanied 
^vith  thunder  and  lightning? 

A.  1st. — Because  the  congelation  of  water 
into  hail  disturbs  the  electricity  of  the  air  ; 
and 

2nd. — The  friction  (produced  by  the  fall 
of  hail)  excite.^  it  still  more. 


MIST,  FOG,  FROST. 


1492. 

Q.  Why  does  hail  fall  generally  in 
mer  and  autumn? 

A.  1st. — Because  the  air  is  more  highly 
dectrified  in  summer  and  autumn  than  j\ 
^"inter  and  spring :  and 

2nd.— The  vapors  in  summer  and  au- 
tumn (being  rarefied)  ascend  to  more  ele- 
vated regions,  which  are  colder  than  those 
nearer  the  earth. 

1493. 

Q.  What  two  things  are  essential  to  caose 
hail  ? 

A.  Two  strata  of  clouds  having  ofpOcute 
electricities,  and  tivo  currents  of  wind.  The 
lower  cloud  (being  negative)  is  the  one  r/;^- 
cipitated  in  hail. 

1494. 

Q.  When  is  the  vapor  of  the  air  or 
clouds  precipitated  in  hail,  rain,  or  snow  ? 

A.  When  the  air  is  saturated  with  onpo}  , 
and  a  cold  current  condenses  it ;  it  is  ti:on 
no  longer  able  to  hold  all  its  vapor  in  y^Shi 
tion,  and  some  of  it  falls  as  rain. 

SECTION  IV.  MIST,  FOG,  FROST. 

1495. 

Q.  What  is  the  cause  of  mist  ^ 


400 


CLOUDS. 


A.  Currents  of  air  from  the  water  com- 
ing in  contact  with  colder  land  currents. 

1496. 

Q.  Why  are  the  currents  of  air  from  the 
land  colder  than  those  blowing  over  water  ? 

A  .  Because  the  earth  radiates  heat  after 
sun-set,  more  freely  than  water,  conse^ 
quently  the  air  which  comes  in  contact  with 
the  land  is  colder  than  that  which  comes  in 
contact  with  the  water. 

1497. 

Q.  Why  are  windows  often  covered  with 
thick  raist^  and  the  frames  wet  with  stand- 
ing water  ? 

A.  Because  the  temperature  of  the  ex- 
ternal air  always  falls  at  sun-set,  and  chills 
the  windoW'glass  with  which  it  comes  in 
contact. 

1498. 

Q.  How  does  this  account  for  the  mist 
and  water  on  a  window  ? 

A.  As  the  warm  vapor  of  the  room 
touches  the  cold  glass  it  is  chilled  and  con- 
densed into  mist ;  and  the  mist  (collecting 
into  drops)  rolls  down  the  window-frame  in 
little  streams  of  water. 

1499. 

Q  Does  the  glass  of  a  window  cool  down 


MIST,  FOG,  FROST.  401 

more  rapidlij  than  the  air  of  the  room 
itself? 

A.  Yes ;  because  the  air  is  kept  ivarm  hy 
fires,  and  by  the  animal  heat  of  the  people 
in  the  room;  in  consequence  of  which,  the 
ftir  of  a  room  suffers  very  little  diminution 
rf  heat  from  the  setting  of  the  sun. 

1500. 

Q.  Whence  arises  the  vapor  of  a  room? 

A.  1st. — The  very  air  of  the  room  con- 
tains vapor  ; 

2nd. — The  breath  and  insensible  perspira- 
tion of  the  inmates  increase  this  vapor;  and 

3rd. — Hot  dinners,  the  steam  of  tea,  and 
so  on,  increase  it  still  more. 

1501. 

Q.  What  is  meant  by  "  the  insensible  per- 
spiration 

A.  From  every  part  of  the  human  body, 
an  insensible  and  invisible  perspiration  issues 
all  night  and  day;  not  only  in  the  hot 
weather  of  summer,  but  also  in  the  coldest 
day  of  winter. 

1502. 

Q.  If  the  perspiration  be  both  inse/inble 
and  invisible  how  is  it  known  that  tJicre  is 
%ny  such  perspiration 

If  you  put  your  naked  arm  ii.io  n 
34* 


402 


CLOUDS. 


dean,  dry  glass  tube,  the  perspiration  will 
condense  on  the  glass  like  mist. 

1503. 

Q.  Why  are  carriage  windows  very  soon 
Cuvered  with  thick  mist? 

A.  Because  the  warm  vapor  of  the  car- 
riage is  condensed  by  the  cold  glass,  and 
covers  it  with  a  thick  mist. 

1504. 

Q.  Why  is  the  glass  window  cold  enough 
to  condense  the  vapor  of  the  carriage  ? 

A.  Because  the  i?iside  of  a  carriage  is 
much  warmer  than  the  outside;  and  the 
glass  window  is  made  cold  by  contact  with 
the  external  air. 

1505. 

Q.  Where  does  the  warm  vapor  of  the 
carriage  come  from  ? 

A.  The  warm  breath  and  insensible  per- 
spiration of  the  persons  riding,  load  the  air 
of  the  carriage  with  warm  vapor. 

1506. 

Q.  What  is  the  cause  of  the  pretty  frost- 
work, seen  on  bed-room  windows  in  winter 
time  ? 

A.  The  breath  and  insensible  perspiritton 
of  the  sleeper  (coming  in  contact  with  the 
loo-cold  window,)  are  frozen  by  the  cold 


MIST,  FOG,  FROST. 


403 


glass,  aud  form  those  beautiful  appearances 
Been  in  our  bed-rooms  on  a  winter  morn- 
ing. 

1507. 

Q.  Why  is  the  glass  of  a  window  colder 
than  the  walls  of  a  room  ? 

A.  Because  glass  is  so  excellent  a  radia^ 
tor^  that  it  parts  with  its  heat  more  rapidly 
than  the  walls  do. 

1508. 

0.  Why  is  a  tumbler  of  cold  water  made 
quite  dull  with  mist,  when  brought  into  a 
room  full  of  people. 

A.  Because  the  hot  vapor  of  the  room  is 
condensed  upon  the  cold  tumbler,  with  which 
it  comes  in  contact ;  and  changes  its  invi- 
sible and  gaseous  form  into  that  of  a  thick 
mist. 

1509. 

Q.  Why  is  a  glass  made  quite  dull  by 
laying  a  hot  hand  upon  it  ? 

A.  Because  the  insensible  perspiration  of 
the  hot  hand  is  condensed  upon  the  cold 
glass,  and  made  perceptible. 

1510. 

Q.  Why  are  wine-glasses  made  quite  duU^ 
when  they  are  brought  into  a  room  full  of 
compini/? 


CLOUDS. 


A.  Because  the  hot  vapor  of  the  room 
(coming  in  contact  with  the  cold  wine- 
glasses) is  condensed  upon  them,  and  covers^ 
tliem  with  vapor,  like  dew. 

1511. 

Q  Why  does  this  misty  appearance  go 
after  a  little  time  ? 

A.  Because  the  glass  becomes  of  the 
isame  temperature  as  the  air  of  the  room ; 
and  will  no  longer  chill  the  vapor  which 
touches  it,  and  condense  it  into  mist. 

1512. 

Q.  Why  is  a  vnne-glass  (which  has  been 
brought  out  of  a  cellar  into  the  air)  covered 
with  a  thick  mist  in  summer  time  ? 

A.  Because  the  vapor  of  the  hot  air  is 
condensed  into  a  thick  mist  by  contact  with 
the  cold  glass. 

1513. 

Q.  Why  does  breathing  on  a  glass  make 
it  quite  dull  ? 

A.  Because  the  hot  breath  is  condensed 
by  tlie  cold  glass;  and  therefore,  covers  it 
with  a  thick  mist. 

1514. 

Q.  Why  are  the  walls  of  a  house  covered 
with  wet  in  a  sudden  thaw  ? 

A   Because  the  walls  (being  thick)  can- 


MIST,  FOG,  FROST. 


405 


not  change  their  temperature,  so  fast  as  the 
air;  in  consequence  of  which,  they  retain 
their  cold  after  the  thaw  has  set  in. 

1515. 

Q.  How  does  ''retaining  their  coW^  ac 
count  for  their  being  so  wet? 

A.  As  the  vapor  of  the  warm  air  touches 
the  cold  walls,  it  is  chilled  and  condensed 
into  water;  which  either  sticks  to  the  walls 
or  trickles  down  in  little  streams. 

1516. 

Q.  Why  does  a  thick  well-built  house  con* 
tj^act  more  damp  of  this  kind  than  an  ordi 
nary  one? 

A.  Because  the  walls  are  much  thicker ; 
and  (if  the  frost  has  penetrated  far  into  the 
bricks)  they  will  be  some  time  before  they 
are  reduced  to  the  same  temperature  as  the 
air. 

1517. 

Q.  Why  are  balusterSy  etc.,  damp  after  a 
thaw? 

A  Because  they  are  made  of  some  very 
close-grained  varnished  wood,  which  can- 
not change  its  temperature  so  fast  as  the  air. 

Balusters — corruptly  called  banisters. 
1518. 

Q.  How  does  this  account  for  the  baluS' 
lers  being  damp? 


406 


CLOUDS. 


A.  The  vapor  of  the  warm  air  (coming 
in  contact  with  the  cold  balusters)  is  chilled 
and  condensed  into  water  upon  them. 

1519. 

Q.  Why  is  our  breath  visible  in  winter  and 
not  in  summer? 

A.  Because  the  intense  cold  condenses 
our  breath  into  visible  vapor ;  but  in  summer 
the  air  is  not  cold  enough  to  do  so. 

1520. 

Q.  Why  are  our  hair  and  the  brim  of  our 
hat  often  covered  with  little  drops  of  pearly 
dew  in  winter  time  ? 

A.  Because  our  breath  is  condensed  as 
soon  as  it  comes  in  contact  with  our  cold 
hair  or  hat,  and  hangs  there  in  little  dew- 
drops. 

1521. 

Q.  What  is  the  cause  of  fog  ? 

A.  If  the  night  has  been  very  calm,  the 
radiation  of  heat  from  the  earth  has  been 
very  abundant;  in  consequence  of  whicli, 
the  air  (resting  on  the  earth)  has  been 
{hilled,  and  its  vapor  condensed  into  a  thick 
mist, 

1522. 

Q.  Why  does  not  the  mist  become  dew? 
A,  Because  the  chill  of  the  air  is  so  rapid. 


mST,  FOG,  FROST. 


40T 


lliat  vapor  is  condensed  faster  than  it  can 
be  deposited;  and  (covering  the  earth  in  a 
mist)  prevents  any  further  radiation  of  heat 
from  the  earth. 

1523. 

Q.  When  the  earth  can  no  longer  radiate 
heat  upwards,  does  it  continue  to  condense 
the  vapor  of  the  air  ? 

A.  No;  the  air  (in  contact  with  the  earth) 
becomes  about  equal  in  temperature  with  the 
surface  of  the  earth  itself ;  for  which  reason 
the  mist  is  not  condensed  into  dew,  but  re- 
mains floating  above  the  earth  as  a  thick 
cloud. 

1524. 

Q.  This  mist  seems  to  rise  higher  and 
higher,  and  yet  remains  quite  as  dense  be- 
low as  at  first.    Explain  the  cause  of  this  ? 

A.  The  air  resting  on  the  earth  is  first 
chilled,  and  chills  the  air  resting  on  it ;  the 
air  which  touches  this  new  layer  of  mist,  be- 
ing also  condensed,  layer  is  added  to  layer ; 
and  thus  the  mist  seems  to  be  rising,  when 
(in  fact)  it  is  only  deepening. 

1525. 

Q.  Why  do  mist  and  dew  vanish,  as  the 
sun  rises  ? 

A.  Because  the  air  becomes  warmer  at 
sun -rise,  and  absorbs  the  vapor. 


408 


CLOUDS. 


1526. 

Q.  What  is  the  cause  of  a  London  fog  ? 

A.  These  fogs  (which  occur  generally  in 
the  winter  time)  are  occasioned  thus: — Some 
current  of  air  (being  suddenly  cooled)  de- 
sands  into  the  warm  streets,  forcing  back  the 
t^nioke  in  a  mass  towards  the  earth. 

1527. 

Q.  Why  are  there  not  fogs  every  night  ? 

A.  Because  the  air  will  always  hold  in 
solution  a  certain  quantity  of  vapor,  (which 
varies  according  to  its  temperature ;)  and, 
when  the  air  is  not  saturated^  it  may  be 
cooled  without  parting  with  its  vapor. 

1528. 

Q.  When  do  fogs  occur  at  night  ? 

A.  When  the  air  is  saturated  with  vapor 
during  the  day.  When  this  is  the  case,  it 
de|)osits  some  of  its  superabundant  moisture 
in  the  form  of  dew  or  fog  as  soon  as  its 
capacity  for  holding  vapor  is  lessened  by 
the  cold  night. 

1529. 

Q.  Why  is  there  very  often  a  fog  over 
marshes  and  rivers,  at  night-time  ? 

A..  Because  the  air  of  marshes  is  al- 
most always  near  saturation;  and,  there- 
fore, the  least  depression  of  temperature  wiW 


MIST,  FOG,  FROST. 


409 


compel  it  to  relinquish  some  of  its  moisture 
in  the  form  of  dew  or  fog. 

1530, 

Q.  Why  does  vapor  sometimes  form  into 
chmdsy  and  sometimes  rest  upon  the  earth 
as  mist  or  fog  ? 

A.  This  depends  on  the  temperature  of 
the  air.  When  the  surface  of  the  earth  is 
warmer  than  the  air,  the  vapor  of  the  earth 
(being  condensed  by  the  chill  air)  becomes 
mist  or  fog.  But,  when  the  air  is  warmer 
than  the  earth,  the  vapor  rises  through  the  air^ 
and  becomes  cloud. 

1531. 

Q.  Why  do  hills ^  etc.,  appear /fl^rg^r  in 
weather  ? 

A.  Because  the  air  is  laden  with  vapor ^ 
which  causes  the  rays  of  light  to  diverge 
more  ;  in  consequence  of  which,  they  pro- 
duce on  the  eye  larger  images  of  objects. 

1532. 

Q.  Why  do  trees,  etc.,  in  wet  weather  ap- 
pear further  off  than  they  really  are. 

A.  Because  the  fog  or  mist  diminishes  the 
light  reflected  from  the  object ;  and  as  the 
object  becr^mes  more  dim,  it  seems  to  be  fur 
fher  of, 

35 


410 


CLOUDS, 


1533. 

Q.  WTiat  is  the  difference  between  a  Jfiist 
and  a  fog  ? 

A.  Mist  is  generally  applied  to  vapors 
condensed  on  marshes,  rivers,  and  lakes. 

Fog  is  generally  applied  to  vapors  con- 
densed on  land;  especially  if  those  vapors 
are  laden  with  smoke. 

1534 

Q.  What  is  the  reason  why  condensed 
vapor  sometimes  forms  into  clouds,  and  some- 
times into  fog? 

A.  If  the  surface  of  the  earth  is  hotter 
than  the  air,  the  vapor  of  the  earth  is  chilled 
by  the  cold  air,  and  becomes  fog;  but  if  the 
air  is  hotter  than  the  earth,  the  vapor  iHses 
through  the  air,  and  becomes  cloud. 

1535, 

Q.  If  cold  air  produces  fog,  why  is  it  not 
foggy  on  a  frosty  morning  ? 

A.  1st. — Because  less  vapor  is  formed  on 
a  frosty  dar/;  and 

2nd. — The  vapor  is  frozen  upon  the 
ground,  before  it  can  rise  from  the  earth, 
a.Tid  becomes  hoar-frost. 

1536. 

Q  Why  are  fogs  more  general  in  avr 
tnmn  than  in  spring  ? 


MIST,  FOG,  FROSl.  411 

A.  The  earth  in  spring  is  not  so  hot  as  it 
is  in  autumn ;  in  consequence  of  which,  its 
vapor  is  not  chilled  into  fog  as  it  issues  into 
tlie  air. 

1537. 

Q  Why  are  fogs  more  common  in  valleys 
lhan  on  hills  ; 

A.  1st. — Because  valleys  contain  more 

moisture  than  hills;  and 

2nd. — They  are  not  exposed  to  sufficient 
wind  to  dissipate  the  vapor. 

1538. 

Q.  How  does  wind  dissipate  fogs  ? 
A.  Either  by  blowing  them  away ;  or  else 
by  dissolving  them  into  vapor  again. 

1539 

Q.  'Wh.dii  is  hoar-frost  ? 
A.  There  are  two  sorts  of  hoar-frost : 
1. — Frozen  dew;  and  2. — Frozen  fog, 

1540. 

Q.  What  is  the  cause  of  the  ground  hoa^^ . 
frost,  or  frozen  dew  ? 

A.  Very  rapid  radiation  of  heat  from  the 
earth  ;  in  consequence  of  which,  the  surface 
is  so  cooled  down,  that  it  freezes  the  dew  con- 
densed upon  it. 


412 


CLOUDS. 


1541. 

Q  Why  is  hoar-frost  seen  only  after  a 
very  clear  night  ? 

A.  Because  the  earth  will  not  have 
thrown  off  heat  enough  by  radiation  to 
freeze  the  vapor  condensed  upon  its  surfacej 
unless  the  night  was  very  clear  indeed. 

1542. 

Q.  What  is  the  cause  of  that  hoar-frost 
which  arises  from  frozen  fog  ? 

A.  The  thick  fog  which  invested  the 
earth  during  the  night  (being  condensed  by 
the  cold  frost  of  early  morning,)  is  congealed 
upon  every  object  with  which  it  comes  in 
contact. 

1543. 

Q.  Why  is  there  little  or  no  hoar-frost 
under  shrubs  and  shady  trees  ? 

A.  1st. — Because  the  leafy  top  arrests 
the  process  of  radiation  from  the  earth ; 

2nd. — Shrubs  and  trees  radiate  heat  to- 
wards the  earth ;  and,  therefore,  the  ground 
beneath  is  never  cold  enough  to  congeal  the 
ittle  dew  which  rests  upon  it. 

Q.  Why  does  hoar-frost  very  often  covet 
the  ground  and  trees^  when  the  water  of 
rivers  is  not  frozen  ? 


ICE. 


413 


A.  Because  it  is  not  the  effect  of  cold  in 
the  air,  but  cold  on  the  surface  of  the  earth 
(produced  by  excessive  radiation,)  which 
freezes  the  dew  condensed  upon  it. 

1545. 

Q.  Why  is  the  hoar-frost  upon  grass  and 
vegetables  much  thicker  than  that  upon  lofty 
trees  ? 

A.  Because  the  air  (resting*  on  the  surface 
of  the  ground)  is  much  colder  after  sun-set 
than  the  air  higher  up  ;  in  consequence  of 
which,  more  vapor  is  condensed  and  frozen 
there. 


CHAP.  IV.— ICE. 

1546. 

Q.  What  is  ice  ? 

A.  Frozen  water.    When  the  air  is  re 
duced  to  thirty-two  degrees  of  heat,  water 
will  no  longer  remain  in  a  fluid  state 

1547. 

Q.  Why  is  solid  ice  lighter  than  water  ? 

A.  Because  water  expands  by  freezing, 
and  as  the  bulk  is  increased,  the  gravity  must 
be  less. 

Nine  cubic  inches  of  water  become  ten  when  lit>zen. 
1548. 

Q.  Why  do  ewers  break  in  a  frosty  night? 
35* 


414 


ICE. 


A.  Because  the  water  in  them  freezes  ^ 
and  {expanding  by  frost)  burst  the  ewers  to 
make  room  for  its  increased  volume. 

1549 

Q  Why  does  it  not  expand  upwards  (like 
)oiling  water,)  and  run  over? 

A.  Because  the  surface  is  frozen  first;  and 
the  frozen  surface  acts  as  a  plug,  which  is 
more  difiicult  to  burst  than  the  porcelain 
ewer  itself. 

1550. 

Q.  Why  do  tiles,  stones,  and  rocks  often 
split  in  winter 

A.  Because  the  moisture  in  them  freezes; 
and  (expanding  by  frost)  splits  the  solid  mass, 

1551. 

Q.  In  winter  time,  foot-marks  and  wheeU 
ruts  are  often  covered  with  an  icy  net-work, 
through  the  interstices  of  which  the  soil  is 
clearly  seen ;  why  does  the  water  freeze  in 
net-work  ? 

A.  Because  it  freezes  first  at  the  sides  of 
the  foot-prints ;  other  crystals  gradually 
shoot  across,  and  would  cover  the  whole 
surface,  if  the  earth  did  not  absorb  the  wa- 
ter before  it  had  time  to  freeze. 

1552. 

Q.  In  winter  time,  these  foot-marks  and 


ICE. 


415 


wheel-ruts  are  sometimes  covered  witii  a  per- 
fect sheet  of  ice,  and  not  an  icy  net-work ; 
why  is  this  ? 

A.  Because  the  air  is  colder  and  the  earth 
harder  than  in  the  former  case ;  in  conse^ 
quence  of  which,  the  entire  surface  of  the 
foot-print  is  frozen  over  before  the  earth 
has  had  time  to  absorb  the  water. 

1553. 

Q.  Why  is  not  the  ice  solid  in  these  ruts? 
— Why  is  there  only  a  very  thin  jUm  or  net- 
work of  ice  ? 

A.  Because  the  earth  absorbs  most  of  the 
water,  and  leaves  only  the  icy  film  behind. 

1554. 

Q.  Why  do  water-pipes  frequently  bm^st 
in  frosty  weather  ? 

A.  Because  the  water  in  them  freezes  ; 
and  {expanding  by  frost)  burst  the  pipes  to 
make  room  for  its  increased  volume. 

1555. 

Q.  Does  not  water  expand  by  heat  as  well 
as  by  cold  ? 

A.  Yes ;  it  expands  as  soon  as  it  is  more 
than  forty- two  degrees,  till  it  boils ;  after 
which  time,  it  flies  off  in  steam.  {See  Fig.  3  ) 


416  ICE. 

FIG.  3. 

Free7ing  water,  32®.  212^,  boiling  watot. 


Here  A  B,  measures  the  bulk  of  a  portion  ol  water  at  forty- two  dsgree* 

It  goes  on  increasing,  in  bulk  to  C  D,  when  it  boils. 

It  also  goes  on  increasing  in  bulk  to  E  F,  when  it  freezes. 

1556. 

Q.  When  does  water  begin  to  expand  from 
cold? 

A.  When  it  is  reduced  to  forty- two  de- 
grees. Water  is  wisely  ordained  by  God  to 
be  an  exception  to  a  very  general  rule — it 
contracts  till  it  is  reduced  to  forty-two  de- 
grees, and  then  it  expands  till  it  freezes. 

The  general  rule  is  this — That  cold  condenses  and  contracts  the  volume 
of  nenrlv  everything  ;  but  water  is  not  contracted  by  cold  after  it  freezes, 
(which  It  does  at  32®.) 

1557. 

Q.  Why  does  water  expand  when  it 
freezes  ? 

A.  Because  it  is  converted  into  solid  crys- 
tals which  do  not  fit  so  closely  as  particles  of 
water  do 

1558. 

Q.  Why  is  the  hottora  of  a  river  nevei 
frozen  ? 


ICE. 


417 


A.  Because  water  ascends  to  the  surface, 
so  soon  as  it  becomes  colder  than  forty-two 
degrees ;  and,  (if  it  freezes)  floats  there  till 
it  is  melted. 

1559. 

Q.  Show  the  wisdom  of  God  in  this  won- 
derful exception  to  a  general  law  7 

A.  If  ice  were  heavier  than  water ^  it  would 
sink  ;  and  a  river  would  soon  become  a  solid 
block  of  ice,  which  could  never  be  dissolved. 

The  general  rule  is — That  all  substances  beoome  heavier  houl  conden- 
iation ;  but  ice  is  lighter  than  water. 

1560. 

Q.  Why  does  not  the  ice  on  the  surjace 
of  a  river  chill  the  water  beneath  and  make 
it  freeze  ? 

A.  1st. — Because  water  is  a  very  bad  con- 
ductor y  and  is  heated  or  chilled  by  convection 
only; 

2nd. — If  the  ice  on  the  surface  were  to 
communicate  its  coldness  to  the  water  be- 
neath, the  water  beneath  would  communi- 
cate its  heat  to  the  ice,  and  the  ice  would  in- 
stantly melt ;  and 

3rd. — The  ice  on  the  surface  acts  as  a 
shield,  to  prevent  the  cold  air  from  penettat-^ 
ing  through  the  river,  to  freeze  the  water 
below  the  surface. 


418 


ICE. 


1561. 

Q.  Why  does  water  freeze  at  the  surjact 
arst? 

A.  Because  the  surface  is  in  contact  with 
Oie  air,  and  the  air  carries  away  its  heat. 

1562. 

Q.  Why  does  the  coat  of  ice  grow  thicker 
and  thicker  if  the  frost  continues  ? 

A.  Because  the  heat  of  the  water  (imme- 
diately below  the  frozen  surface)  passes 
through  the  pores  of  the  ice  into  the  cold  air. 

1563. 

Q.  Why  are  not  whole  rivers  frozen  (layer 
by  layer,)  till  they  become  solid  ice  ? 

A.  Because  water  is  so  slow  a  conductor, 
that  our  frosts  never  continue  long  enough  to 
convert  a  whole  river  into  a  solid  mass  of 
ice. 

1564. 

Q.  Why  does  not  running  water  freeze  so 
fast  as  still  water? 

A.  1st. — Because  the  motion  of  the  cur* 
rent  disturbs  the  crystals,  and  prevents  their 
forming  into  a  continuous  surface ;  and 

2nd. — The  heat  of  the  under  surface  is 
communicated  to  the  upper  surface  by  the 
•"oiling  of  the  wnier. 


ICE* 


419 


1565. 

Q.  When  running  water  is  frozen,  why  is 
rhe  r:e  generally  very  rough? 

A.  Because  little  flakes  of  ice  are  first 
formed  and  carried  down  the  stream,  till  they 
meet  some  obstacle  to  stop  them ;  other  flakes 
of  ice  (impinging  against  them)  are  arrested 
in  like  manner ;  and  the  edges  of  the  differ- 
ent flakes  overlapping  each  other,  make  the 
surface  rough. 

1566. 

Q.  Why  do  some  parts  of  a  river  freeze 
less  than  others  ? 

A.  Because  springs  issue  from  the  bot- 
tom ;  and  (as  they  bubble  upwards)  thaw 
the  ice,  or  make  it  thin. 

1567. 

Q.  When  persons  fall  into  a  river  in  win- 
ter time,  why  does  the  water  feel  remarka- 
bly ivarm  ? 

A.  Because  the  frosty  air  is  at  least  ten 
or  twelve  degrees  colder  than  the  water  is. 

Tao  -Titer  below  the  surface  at  least  42°  ;  but  the  air  32°,  or  even 
less. 

1568. 

Q.  Why  is  shallovj  water  frozen  more 
quickly  than  deep  water  ? 

A.  Because  the  whole  oolume  of  ^vater 
must  be  cooled  to  forty-two  degrees,  before 


420 


ICE. 


he  surface  can  he  frozen;  and  it  takes  a 
longer  time  to  cool  down  a  deep  bed  of  wa- 
ter than  a  shallow  one. 

1569. 

Q.  Why  is  sea-water  rarely  frozen  ? 

A.  1st. — Because  the  mass  of  water  is  so 
great,  that  it  requires  a  very  long  time  to 
cool  the  whole  volume  down  to  forty-two 
degrees. 

2nd. — The  ebb  and  flow  of  the  sea  inter- 
fere with  the  cooling  influence  of  the  air;  and 

3rd. — Salt  water  never  freezes  till  the 
surface  is  cooled  down  twenty-five  degrees 
below  freezing  point. 

1570. 

Q.  Why  do  some  lakes  rarely  (if  ever) 

freeze  ? 

A.  1st. — Because  they  axe  very  deep  ;  and 
2nd. — Because  their  water  is  supplied  by 
springs,  which  bubble  from  the  bottom. 

1571. 

Q.  Why  does  the  depth  of  water  retard  its 

freezing? 

A.  Because  the  whole  volume  of  vmter  must 
be  reduced  to  forty-two  degrees,  before  the 
mrface  will  freeze  ;  and  the  deeper  the  wa- 
ter, the  longer  it  will  be  before  the  whole 
volume  is  thus  reduced. 


ICE. 


421 


1572. 

Q.  Whj  do  springs  at  the  bottom  of  a 
lake  prevent  its  freezing  ? 

A.  Because  they  keep  continually  send- 
ing forth  fresh  water,  which  prevents  the 
lake  from  being  reduced  to  the  necessary 
dogree  of  coldness. 

1573. 

Q.  It  is  colder  in  a  thaWy  than  in  a  frost. 
Explain  the  reason  of  this  ? 

A.  When  frozen  water  is  thawed,  it  absorbs 
heat  from  the  air,  etc.,  to  melt  the  ice ;  in 
consequence  of  which,  the  heat  of  the  air  is 
greatly  reduced. 

1574. 

Q.  It  is  warmer  in  a  frost  than  in  a  thaw. 
Explain  the  reason  of  this  ? 

A.  When  water  freezes,  it  gives  out  la- 
ient  heat,  in  order  that  it  may  be  converted 
into  solid  ice;  and,  as  much  heat  is  liberated 
from  the  water  to  the  atmosphere,  the  air 
feels  warmer. 

1575. 

Q.  Salt  dissolves  ice.  Explain  the  reason 
of  this? 

A.  Water  freezes  at  32"*,  but  salt  and  wa- 
ter will  r.ot  freeze  till  the  air  is  twenty-fivo 
36 


422 


ICE, 


flegrees  colder;  if,  therefore,  salt  be  added 
to  frozen  water,  it  dissolves  it. 

Unless  the  thermometer  stands  below  7° 
1576. 

Q.  Will  any  thing  dissolve  ice  except  ^a//? 
A.  Yes ;  any  acid,  such  as  sulphuric  acid, 
ftitric  acid,  etc. 

1577. 

Q.  Why  is  a  mixture  of  salt  and  snow 
colder  than  snow  itself  ? 

A.  Because  salt  dissolves  the  crystals  of 
snow  into  a  fluid ;  and  whenever  a  solid  is 
converted  into  a  fluid,  heat  is  absorbed^  and 
the  cold  made  more  intense. 

1578. 

'  Q.  Why  does  frost  make  the  earth  crack? 
A.  Because  the  water  absorbed  by  the 
earth  in  warm  weather,  expanding  by  the 
frost,  thrusts  the  particles  of  earth  apart 
from  each  other,  and  leaves  a  chink  or  crack 
between. 

1579. 

Q.  Show  the  wisdom  of  God  in  this 
arrangement  ? 

A.  These  cracks  in  the  earth  let  in  au% 
dew,  rain,  and  many  gases  favorable  to 
vegetation. 

1580. 

Q,  Why  does  the  earth  crumble  in  spring? 


ICE. 


428 


A.  Because  the  ice  of  the  clods  dissolves ; 
and  the  particles  of  earth  (which  had  been 
thrust  apart  by  the  frost)  being  left  unsup- 
portea,  tumble  into  minute  parts,  because 
their  cement  of  ice  is  dissolved. 

1581. 

Q.  Why  does  mortar  crumble  away  in 
frost? 

A  Because  it  was  not  dried  in  the  warm 
weather;  therefore,  its  moisture  freezes,  ex 
pands,  and  thrusts  the  particles  of  the  mor- 
tar away  from  each  other ;  but  as  soon  as 
the  frost  goes,  the  water  condenses,  and  leaves 
the  mortar  full  of  cracks  and  chinks. 

1582. 

Q.  Why  does  stucco  peel  from  a  wall  in 
frosty  weather 

A.  Because  the  stucco  was  not  dried  in 
the  warm  weather ;  therefore,  its  moisture 
freezes,  expands,  and  thrusts  its  particles 
away  from  the  wall ;  but,  as  soon  as  the 
water  condenses  again  by  the  thaw,  the 
stucco  (being  unsupported)  falls  by  its  mm 
weight. 

1583. 

Q.  Why  cannot  bricklayers  and  plasterers 
work  in  frosty  weather  ? 

A.  Because  frost  expands  mortar,  and 


424 


ICE. 


causes  the  bricks  and  plaster  to  start  from 
their  position. 

1584. 

Q.  Why  do  bricklayers  cover  their  work 
with  straw  in  spring  and  autumn  ? 

A.  Because  straw  is  a  non-conductor; 
and  prevents  the  mortar  of  their  new  work 
from  freezing,  during  the  cold  nights  of 
spring  and  autumn. 

1585. 

Q.  Why  are  water  pipes  often  covered 
with  straw  in  winter  time  ? 

A.  Because  straw  (being  a  non-conductor) 
-prevents  the  water  of  the  pipes  from  freezing, 
and  the  pipes  from  bursting. 

1586. 

Q.  Why  are  delicate  trees  covered  with 
straiv  in  winter  ? 

A.  Because  straw  (being  a  non-conductor) 
prevents  the  sap  of  the  tree  from  being 
frozen. 

1587. 

Q.  Can  water  be  frozen  in  any  way 
sides  by  frosty  weather  ? 

A.  Yes ;  in  very  many  ways.  For  ex- 
ample— a  bottle  of  water  wrapped  in  cotton, 
and  frequently  wetted  with  ether  will  soon 
freeze. 


ICE. 


425 


1588. 

Q.  Why  would  water  f  reeze  if  the  bottle 
were  kept  constantly  wetted  with  ether  ? 

A.  Because  evaporation  would  carry  off 
the  heat  of  the  water,  and  reduce  it  to  the 
freezing  point. 

1589. 

Q.  Why  does  ether  freeze  under  the  r^- 

ceiver  of  an  air-pump ^  when  the  air  is  ex- 
hausted? 

A.  Because  evaporation  is  very  greatly  in- 
creased by  the  diminution  of  atmospheric  pres- 
sure; and  the  ether  freezes  by  evaporation. 

FREEZING  MIXTURES. 

0     1.  If  nitre  be  dissolved  in  water,  the  heat  of  the  liquid  will  be  reduced 
sixteen  degrees. 

2.  If  five  ounces  of  nitre,  and  five  of  sal-ammoniac  (both  finely  pow- 
dered) be  dissolved  in  nineteen  ounces  of  water,  the  heat  of  the  liquid  will 
be  reduced  forty  degrees. 

3.  If  three  pounds  of  snow  be  added  to  one  pound  of  salt,  the  mixture 
will  fall  to  00  (or  thirty-two  degrees  below  freezing  point.) 

The  two  following  are  the  coldest  mixtures  yet  known — 

1.  Mix  three  pounds  of  muriate  of  lime  with  one  pound  of  snow. 

2.  Mix  five  pounds  of  diluted  sulphuric  acid  with  four  pounds  of  snow 

1590. 

Q.  Is  salt  and  snow  really  colder  than 
enow? 

A.  Yes,  many  degrees  colder;  so  that 
by  dipping  your  hand  into  the  mixture  ^zr^^^, 
and  into  snow  afterwards^  the  snow  will  seem 
to  be  comparative!)  warm. 
36* 


426 


ICE. 


1591. 

Q.  Can  we  be  made  to  feel  the  heat  ol 
ice  or  snow  ? 

A  Yes ;  into  a  pint  of  snow,  put  half  ^^ 
pint  of  salt ;  then  plunge  your  hand  into 
the  liqaid,  it  will  feel  so  intensely  cold,  thai 
the  snow  itself  will  seem  tvarm  in  compari- 
son to  it. 


# 


PART  VL 

OPTICS. 


CHAP.  I.— LIGHT 

1592. 

Q.  Wliat  is  light? 

A.  Rapid  undulations  of  a  fluid  called 
ether,  made  sensible  to  the  eye  by  striking 
on  the  optic  nerve. 

1593. 

Q.  How  fast  does  light  travel  ? 

A.  Light  travels  so  fast,  that  it  would 
go  eight  times  round  the  earth  while  a  per- 
son counts  ^^one.^^ 

1594. 

Q.  Wha^t  is  ether? 

A.  A  very  subtle  fluid,  which  pervades 
and  surrounds  every  thing  we  see. 

N.  B.  This  theory  of  light  is  not  altogether  satisfactory,  but  has  been 
retained  as  the  most  plausible  hitherto  projected. 

1595. 

Q.  How  can  undulations  of  ether  produce 
light? 

A.  As  sound  is  produced  by  undulations 
Oj  air  striking  on  the  ear,  so  light  is  pro 

427 


428 


LIGHT. 


duced  by  undulations  of  ether  striking  on 
the  eye. 

1596. 

Q.  How  does  combustion  make  undula- 
tions of  light  ? 

A.  The  atoms  of  matter  (set  in  motion 
by  lieat)  striking  against  this  ether,  produce 
undulations  in  it;  as  a  stone  thrown  into  a 
Btream  produces  undulations  in  the  water. 

1597. 

Q.  Does  all  light  travel  equally  fast  ? 

A.  Yes ;  the  light  of  the  sun — the  light 
of  a  candle — or  the  light  from  houses,  trees, 
i\xA  fields, 

1598. 

Q.  Where  does  the  light  of  houses,  trees 
aad  fields y  come  from  ? 

A.  The  light  of  the  sun  (or  of  some  lamp 
or  candle)  is  reflected  from  their  surfaces. 

1599. 

Q.  Why  are  some  surfaces  brilliant  (like 
glass  and  steel,)  and  others  dull,  like  lead  ? 

A.  Those  surfaces  which  reflect  the  most 
tight y  are  the  most  brilliant;  and  those  which 
absorb  light  are  dull. 

1600. 

Q  What  is  meant  by  reflecting  light  1 


LIGHT 


429 


A.  Throwing  the  rays  of  light  back  again 
from  the  surface  on  which  they  fall. 

1601. 

Q.  What  is  meant  by  absorbing  light  ? 

A.  Retaining  the  rays  of  light  on  the 
surface  on  which  they  fall ;  in  consequence 
of  which,  their  presence  is  not  made  sen- 
sible by  reflection. 

1602. 

Q.  Why  can  a  thousand  persons  the 
same  object  at  the  same  time  ? 

A.  Because  it  throws  off  from  its  sur- 
face an  infinite  number  of  rays  in  all  direc- 
tions ;  and  one  person  sees  one  portion  of 
these  rays,  and  another  person  another. 

1603. 

Q.  Why  is  the  eye  pained  by  a  sudden 
light? 

A.  Because  the  nerve  of  the  eye  is  bur 
dened  with  rays  before  the  pupil  has  had 
time  to  contract. 

1604. 

Q.  Why  does  it  give  us  pain  if  a  candle 
be  brought  suddenly  towards  our  bed  at 
night-time  ? 

A.  Because  the  pupil  of  the  eye  dilates 
very  much  in  the  dark,  in  order  to  admit 
more  rays-    When,  therefore,  a  candle  is 


m 


LiQm. 


brought  suddenly  before  us,  the  enlarged 
pupils  overload  the  optic  nerves  with  rays 
^hich  causes  pain. 

1605. 

Q.  Why  can  we  bear  the  candle-light  af 
ter  a  few  moments  ? 

A.  Because  the  pupils  contract  again  al 
most  instantly;  and  adjust  themselves  tc 
the  quantity  of  light  which  falls  upon  them. 

1606. 

Q.  Why  can  we  see  nothing,  when  we  leave 
a  well-lighted  room,  and  go  into  the  darker 
road  or  street  ? 

A.  Because  the  pupil  (which  contracted 
in  the  bright  room)  does  not  dilate  instan- 
taneously ;  and  the  contracted  pupil  is  not 
able  to  collect  rays  enough  from  the  darker 
road  or  street  to  enable  us  to  see  objects 
before  us. 

1607. 

Q.  Why  do  we  see  better  when  we  get 
used  to  the  dark  ? 

A.  Because  the  pupil  dilates  again,  and 
allows  more  rays  to  pass  through  its  aper- 
ture ;  in  consequence  of  which,  we  see 
more  distinctly. 

Thus,  when  the  lamp  tnat  lighted 

The  trav'ler  at  first  goes  out, 
He  feels  awhile  benighted 

A.nd  lingers  on  ui  fear  and  doubt 


LIGHT. 


43i 


But  soon  the  prospect  clear.ng, 

In  cloudless  starlight  on  he  treads, 
And  finds  no  lamp  so  cheering 

As  that  light  which  heav'n  sheds. — Thmnas  Moore, 

1608. 

Q.  If  we  look  at  the  su7i  for  a  few  mo- 
ments, why  do  all  other  things  appear  dark? 

A.  Because  the  pupil  of  the  eye  becomes 
so  much  contracted  by  looking  at  the  sun, 
that  it  is  too  small  to  collect  sufl&cient  rays 
from  other  objects  to  enable  us  to  distin- 
guish their  colors.  {See  "Accidental  co- 
lors.") 

1609. 

Q.  If  we  watch  a  bright  fire  for  a  few 
moments,  why  does  the  room  seem  dark? 

A.  Because  the  pupil  of  the  eye  becomes 
so  much  contracted  by  looking  at  the  fire, 
that  it  is  too  small  to  collect  sufficient  rays 
from  the  objects  around  to  enable  us  to  dis- 
tinguish their  colors. 

1610. 

Q  .  Why  can  we  see  the  proper  colors  of 
f^very  object  again,  after  a  few  minutes  ? 

A.  Because  the  pupil  dilates  again  and 
accommodates  itself  to  the  light  around. 

1611 

Q.  Why  can  tigers ^  cats,  and  owls,  see  in 
the  dark  ? 

A.  Because  they  have  the  power  of  ?n 


432 


LIGHT. 


larging  the  pupil  of  their  eyes  so  as  to  collect 
several  scattered  rays  of  light;  in  conse- 
quence of  which,  they  can  see  distinctly 
when  it  is  not  light  enough  for  us  to  see 
any  thing  at  alh 

1612. 

Q.  Why  do  cats  and  owls  sleep  almost  all 

day? 

A.  Because  the  pupil  of  their  eyes  is 
very  broad,  and  daylight  fatigues  them ;  so 
they  close  their  eyes  for  relief. 

1613. 

Q.  Why  do  cats  keep  winking  when  they 
sit  before  a  fire  ? 

A.  Because  the  pupil  of  their  eye  is 
very  broad,  and  the  light  of  the  fire  is  pain- 
ful ;  so  they  keep  shutting  their  eyes  to  re- 
lieve the  sensation  of  too  much  light. 

1614. 

Q.  Why  do  tigers,  cats,  owls,  etc.,  prowl 
by  night  for  prey  ? 

A.  Because  they  sleep  all  day  when  the 
strong  light  would  be  painful  to  them;  and 
as  they  can  see  clearly  in  the  dark,  they 
prowl  then  for  prey. 

1615. 

Q.  Why  do  glow-worms  and  fire-flies,  gli»- 
len  by  night  only  ? 


LiaHT. 


433 


A.  Because  the  light  of  day  is  strong 
tiiat  it  eclipses  the  feeble  light  of  a  glow- 
worm or  fire-fly ;  in  consequence  of  which, 
glow-worms  are  invisible  by  day. 

1616. 

Q  Why  can  we  not  see  the  stars  in  the 
i  ay 'time? 

A.  Because  the  light  of  day  is  so  pow- 
erful that  it  eclipses  the  feeble  light  of  the 
stars ;  in  consequence  of  which,  they  are 
invisible  by  day. 

1617, 

Q.  Why  can  we  see  the  stars  even  at 
mid-day^  from  the  bottom  of  a  deep  well  ? 

A.  Because  the  light  of  the  stars  is  not 
overpowered  by  the  rays  of  the  sun,  which 
are  lost  in  the  numerous  reflections  which 
they  undergo  in  the  well. 

The  rays  of  the  sun  will  enter  the  well  very  obliquely  ;  whereas,  many 
stars  will  shine  directly  over  the  well. 

1618. 

Q.  What  is  the  use  of  two  eyes^  smce  they 
present  only  one  image  of  any  object  ? 

A.  To  increase  the  light — or  to  take  in 
more  rays  of  light  from  the  object  looked 
at,  in  order  that  it  may  appear  more  dis- 
tinct. 

1619. 

Q.  Why  do  we  not  see  things  double,  with 
two  eyes  ? 

37 


134 


LIGHT. 


A.  1st. — Because  the  axis  of  both  eyea 
s  IB  turned  to  one  object;  and,  therefore,  the 
same  impression  is  made  on  the  retina  of 
each  eye :  and 

2nd. — Because  the  nerves  (which  receivf 
the  impression)  have  one  point  of  union  be- 
fore  they  reach  the  brain.  - 

This  is  not  altogether  satisfactory,  although  it  is  the  explanation  g«*fia 
rally  given.  The  phenomenon  probably  is  rather  psychological  than  ma- 
terial. 

1620. 

Q.  Why  do  we  see  ourselves  in  a  glass  ? 

A.  Because  the  rays  of  light  from  our 
face  strike  against  the  surface  of  the  glass, 
and  (instead  of  being  absorbed)  are  re- 
flected, or  sent  back  again  to  our  eye 

1621. 

Q.  Why  are  the  rays  of  light  reflected  by 
a  mirror  ? 

A.  Because  they  cannot  pass  through  the 
impenetrable  metal  with  which  the  back  of 
the  glass  is  covered  ;  so  they  rebound  back 
just  as  a  marble  would  do,  if  it  were  thrown 
against  a  wall. 

1622. 

Q.  IVhen  a  marble  is  rolled  towards  a 
wall,  what  is  the  path  through  which  it  runt 
called  ? 

A  The  line  of  incidence. 


LIGHT.  435 
1623, 

Q.  When  a  marble  rebounds  back  again 
what  is  the  path  it  then  describes  called  ? 
A>  The  line  of  reflection. 

(See  Fig,  4.)  If  A  B,  be  the  line  of  incidence,  then  B  C,  is  the  line 
reflection  ;  and  vice  versa. 

1624. 

Q.  When  the  light  of  our  face  goes  to 
Uie  glass,  what  is  the  path  through  which 
it  goes  called  ? 

A.  The  line  of  incidence. 

1625. 

Q.  When  the  light  of  our  face  is  reflected 
back  again  from  the  mirror,  what  is  this  re- 
turning  path  called  ? 

A.  The  line  of  reflection. 

K 1626. 

Q.  What  is  the  angle  of  incidence  ? 
A.  The  angle  between  the  line  of  inci* 
dence  and  the  perpendicular. 

1627, 

Q.  What  is  the  angle  of  reflection  ? 
A.  The  angle  between  the  line  of  refj^o 
Hon  and  the  perpendicular.    {See  Fig.  4.) 


436 


LIGHT. 


S  B  S 


Let  S  S,  be  any  surface,  P  B,  a  perpendicular  to  it.  If  a  marble  were 
\hrown  from  A  to  B,  and  bomided  back  to  C  ;  then  A  B  P,  would  be 
called  the  angle  of  incidence,  and  C  B  P,  the  angle  of  reflection* 

1628. 

Q.  Why  does  our  reflection  in  a  mirror 
8eem  to  approach  us,  as  we  walk  towards  it; 
and  to  retire  from  us,  as  we  retire  ? 

A.  Because  the  lines  and  angles  of  inci- 
dence  are  always  equal  to  the  lines  and  an- 
gles of  reflection  ;  in  consequence  of  whii^.b, 
the  image  will  always  seem  to  be  as  far  he- 
hind  the  mirror  as  the  real  object  is  hefon  it. 
riG.  5. 

K  0  C  C 


LIGHT. 


437 


Siippose  A  to  be  a  mirror — C  A,  E  A  and  D  A,  F  A^  the  lines  of  inci- 
dence ;  then  G  A,  K  A,  and  H  A,  L  A,  are  the  lines  of  retietlion.  When 
the  arrow  is  at  C  D,  its  image  wiil  appear  at  G  H,  because  line  C  A=G  A, 
and  line  D  A,=  H  A ;  and  also  the  an<^le  C  A  B,=a)igle  G  A  U,  and  an- 
^le  D  A  B,=H  A  B.  For  a  similar  reason,  if  the  arrow  were  at  E  F,  the 
image  would  seem  to  be  at  K  L. 


Q.  Why  can  a  man  see  his  whole  person. 
reflected  in  a  little  mirror^  not  six  inches  in 
length  ? 

A.  Because  the  lines  and  angles  of  inci- 
dence are  always  equal  to  the  lines  and  an- 
gles of  reflection;  in  consequence  of  which, 
his  image  will  seem  to  be  as  far  behind  the 
mirror  as  his  person  is  before  it. 


Take  the  last  figure  ;  C  D,  is  much  larger  than  the  mirror  A  ;  but  tha 
head  of  the  arrow  C,  is  reflected  obliquely  behind  the  mirror  to  G  ;  and 
ihe  barb  D,  appears  at  H.  Why  ?  Because  line  C  A  ,=G  A,  and  hn<j 
D  A,=H  A;  also  theangle  C  A  B=angle  G  AB,  and  angle  D  A  B,=H  A  B. 


Q.  Why  does  the  image  of  any  object  in 
water  always  appear  inverted  ? 

A.  Because  the  angles  of  incidence  ar() 
always  equal  to  the  angles  of  reflection  ? 


1629. 


1630. 


FIG.  6. 


A 


37» 


438 


LIGHT. 


Here  the  arrow-head  A,  strikes  the  water  at  F,  and  is  reflected  to  D, 

and  the  barb  B,  strikes  ihe  water  at  E,  and  is  reflected  to  C. 

If  a  spectator  stands  at  G,  he  will  see  the  reflected  lines  C  E,  and  D  F, 
produced  as  far  as  G. 

It  is  very  plain,  that  A,  (the  more  elevated  object)  will  strike  the  water^ 
ni:'d  be  projected  from  it  more  perpendicularly  than  the  point  B;  and, 
fherefore,  the  image  will  seem  inverted. 

1631. 

Q.  When  we  see  our  reflection  in  watery 
why  do  we  seem  to  stand  on  our  head? 

A.  Because  the  angles  of  incidence  are 
always  equal  to  the  angles  of  reflection. 

Suppose  our  head  to  be  at  A,  and  our  feet  at  B  ;  then  the  shadow  of  ouf 
head  will  be  seen  at  D,  and  the  shadow  of  our  feet  at  C.    {See  jig*  6.) 

1632. 

Q.  Why  do  windows  seem  to  hlaze  at  sun- 
rise and  sun-set  ? 

A.  Because  glass  is  a  good  reflector  of 
light;  and  the  rays  of  the  sun  (striking 
against  the  window-glass)  are  reflected,  or 
thrown  back. 

1633. 

Q.  Why  do  not  windows  reflect  the  noon- 
day  rays  also  ? 

A.  They  do,  but  the  reflection  is  not  seen. 

1634. 

Q.  Why  is  the  reflection  of  the  rising  and 
setting  sun  seen  in  the  window,  and/zo/  that 
of  the  noon-day  sun  ? 

A.  Because  the  rays  of  the  noon-day  sun 
enter  the  glass  too  obliquely  for  their  reflec- 
tion to  be  seen. 


LIQHI,  *39 


Sun  near  the  hori&cm. 


In  Ike  preceding  cut,  A  B,  represents  a  ray  of  the  noon-day  sun  striking 
Ihe  window  at  B  ;  its  reflection  will  be  at  C. 
But  D  B,  (a  ray  of  the  rising  or  setting  sun)  will  be  reflected  to  E,  (th« 

eye  of  the  spectator.) 

1635. 

Q.  Why  can  we  not  see  the  reflection  of 
the  sun  in  a  well,  during  the  day-time  ? 

A.  Because  the  rays  of  the  sun  fall  so  ob- 
liquely that  they  never  reach  the  surface  of 
the  water  at  all,  but  strike  against  the  brick 
sides. 


440 


LIGHT. 


Fia.  B. 


Le".  B  E  D  C,  be  the  well,  and  D  E,  the  water. 
The  ray  A  B,  strikes  against  the  brick-work  inside  the  wall :  aad 
The  ray  A  C,  strikes  ag-ainst  the  brick-work  outside  the  well. 
None  will  ever  touch  the  water  D  E. 

1636. 

Q.  Why  are  stars  reflected  in  a  wellj  al» 
(liough  the  sun  is  not? 

A.  Because  the  rays  of  those  stars,  which 
pass  nearl}^  over-head,  will  not  fall  so  ob- 
liquely into  the  well  as  the  rays  of  the  sun, 


LIGHT. 


411 


FIG.  9. 
The  moon  or  a  etor. 

A 


Here  the  star's  rays  A  B,  A  C,both  strike  the  water  D  E,  and  are  re 
ttected  by  it. 

1637. 

Q.  On  a  lake  of  water,  the  moon  seems 
to  make  a  path  of  light  towards  the  eye  of 
the  spectator,  while  all  the  rest  of  the  lake 
seems  dark — why  is  this  ? 

A-  Because  the  lake  is  in  deep  shadow; 
and  many  rays  which  would  be  eclipsed  by 
the  broad  light  of  day  become  visible. 

The  same  path  of  light  may  be  discerned  in  the  day-time,  when  a  cloud 
passes  over  the  sun. 

1638. 

Q.  Tn  a  sheet  of  water  at  noon,  the  sun  ap- 
pears to  shine  upon  only  one  spot^  and  all  the 
rest  of  the  water  seems  dark — why  is  this 

A.  Because  the  ravs  fall  at  various  de 


442 


LIGHT. 


grees  of  obliquity  on  the  water,  and  are  re- 
flected at  similar  angles;  but  as  only  those 
which  meet  the  eye  of  the  spectator  are  visible, 
all  the  water  will  appear  dark  except  that  one 
vpor, 

FIG.  10 


Here,  of  the  rays  S  A,  S  B,  and  S  C,  only  the  ray  S  C,  meets  the  eye 

Df  the  spectator  D 

The  spot  C,  therefore,  will  appear  luminous  to  the  spectator  D,  but  no 
other  spot  of  the  water  ABC. 

1639. 

Q.  Wliy  are  more  stars  visible  from  a 
mountain  than  from  a  plain  ? 

A.  Because  they  have  less  air  to  pass 
through .  As  air  absorbs  and  diminishes  ligh  t ; 
therefore,  the  higher  we  ascend,  the  less 
light  will  be  absorbed. 

1640. 

Q.  Why  do  the  svn  and  moon  seem  larger 


LIGHT.  443 

at  their  rising  and  setting,  than  at  any  other 
time  ? 

A.  Because  the  arch  of  the  sky  (in  which 
the  sun  and  moon  are  seen)  is  further  dis- 
Unt  at  the  horizon  than  it  is  over-head. 

FIG.  II. 


Let  M,  M,  be  the  orbit  of  the  sun  or  moon, 

I«t  B,  D,  be  the  arch  of  the  sky,  in  which  the  sun  and  moon  aic 
*/  us. 

ll  will  bo  seen  from  the  figure,  that  the  sur  or  moon  at  the  horizon  will 
appear  much  larger,  because  C,  D,  is  longer  than  C,  B. 

The  Phenomenon  referred  to  above,  (called  the  horizontal  Sun  and 
Moon,)  has  perplexed  philosophers  to  the  present  hour.  The  solution  given 
IS  not  altogether  satisfactory — Sir  J,  Herschell  says,  "  The  dilated  size  of 
.he  sun  or  moon,  when  seen  near  the  horizon,  has  nothing  to  do  with  rg- 
fraction.  It  is  an  illusion  of  the  Judgment,  arising  from  the  terrestrial  ob- 
jects interposed,  or  placed  in  comparison  with  them.  Actual  measurement 
with  a  proper  instrument  corrects  our  error,  without,  however,  dippellinjr 
vu  iUueion-— the  whole  is  owing  to  the  effeot  of  iiarallaxV 


LIGHT. 


1641. 

Q.  Why  can  we  not  set  into  the  street  oi 
road  when  candles  are  lighted  ? 

A  1st. — Because  glass  is  a  reflector,  and 
Ihrows  the  candle-light  back  into  the  room 
ngain ;  and 

2nd. — The  pupil  of  the  eye  (having  be- 
come contracted  by  the  light  of  the  room)  is 
too  small  to  collect  rays  enough  from  the 
dark  street  to  enable  us  to  see  into  it. 

1642. 

Q.  Why  do  we  often  see  the  fire  reflected 
in  our  parlor  window  in  winter  time  ? 

A.  Because  glass  is  a  good  reflector;  and 
the  rays  of  the  fire  (striking  against  the 
window- glass)  are  reflected  back  into  the  room 
again. 

1643. 

Q.  Why  do  we  often  see  the  image  of 
our  candles  in  the  window,  while  we  are 
sitting  in  our  parlor  ? 

A.  Because  the  rays  of  the  candle  (strik- 
ing against  the  glass)  are  reflected  back  info 
the  room;  and  the  darker  the  night,  the 
clearer  the  reflection. 

1G44. 

Q.  Why  is  this  reflection  more  clear,  if 
the  external  air  be  dark  ? 


LIGHT. 


445 


A.  Because  the  reflection  is  not  eclipsed 
hy  the  brighter  rays  of  the  sun  striking  on 
ike  other  side  of  the  window 

1645. 

Q.  If  the  shadow  of  an  object  be  thrown 
on  a  wall — the  closer  the  object  is  held  to 
the  candle,  the  larger  will  be  its  shadow. 
Why  is  this  ? 

A.  Because  the  rays  of  light  diverge  (from 
the  flame  of  a  candle)  in  straight  lines  like 
lines  drawn  from  the  centre  of  a  circle 


PIG.  12. 


Here  the  arrow  A,  held  close  to  the  candie,  wiii  cast  the  shadow  B  P; 
on  a  wall ;  while  the  same  arrow  held  at  C,  would  cast  only  the  liltla 
shadow  D  E. 

1646. 

Q,  When  we  enter  a  long  avenue  of  trees, 
why  does  the  avenue  seem  to  get  narrower 
and  narrower,  till  the  two  sides  appear  to 
meet? 

38 


4  40  LIGHT. 

A.  Because  the  further  the  trees  are  off, 
the  more  acute  will  be  the  angle  that  any  op- 
posite two  make  with  our  eye. 

PIG.  13. 


Here  the  width  between  the  trees  A  and  B,  will  seem  to  be  as  great  ai 
the  line  A  B. 

Bui  the  width  between  the  trees  C  and  D  will  seem  to  be  no  more  than 
E  F. 

1647. 

Q.  In  a  long,  straight  street,  why  do  the 
houses  on  the  opposite  sides  seem  to  ap- 
proach nearer  together  as  they  are  more  dis- 
tant? 

A.  Because  the  more  distant  the  houses 
are,  the  more  acute  will  be  the  angle  which 
any  opposite  two  make  with  our  eye. 

Thus  in  fig.  13  :  If  A  and  B,  were  two  houses  at  the  top  of  the  street, 
the  street  would  seem  to  be  as  wide  as  the  line  A  B. 

And  if  C  and  D,  were  two  houses  at  the  bottom  of  the  street,  the  stre«{ 
fe«re  would  seem  to  be  no  wider  than  E  F. 

1648. 

Q.  In  an  avenue,  why  do  the  t/'ees  seem 
to  be  smaller  as  their  distance  increases  ? 

A.  Because  the  further  the  trees  are  of, 
the  more  acute  will  be  the  angle  made  by 
their  perpendicular  height  with  our  eye. 


LIGHT  447 
FIG.  3  4. 


Here  the  first  tree  A  B,  will  appear  the  height  of  the  line  A  B  ;  but  the 
last  tree  C  D,  will  appear  only  as  high  as  the  line  E  F. 

1649. 

Q.  In  a  long,  straight  street,  why  do  the 
houses  seem  to  be  smaller  and  smaller,  the 
further  they  are  off? 

A.  Because  the  further  any  house  is  off, 
the  more  acute  will  he  the  angle  made  by  its 
perpendicular  height  with  our  eye. 

Thus  in  fig.  14  :  If  A  B,  be  a  house  r.t  the  top  of  ihe  street,  its  perpeudLcu 
lar  height  will  be  that  of  the  line  A  B. 

If  C  D,  be  a  house  at  the  bottom  of  the  street,  its  perpendicular  height 
will  appear  to  be  that  of  E  F. 

1650. 

Q.  Why  does  a  man  on  the  top  of  a  moun- 
tain, or  church  spire,  seem  to  be  no  bigger 
than  a  crow  ? 

A.  Because  the  angle  made  in  our  eye  by 
the  perpendicular  height  of  the  man  at  that  dis- 
tance, is  no  bigger  than  that  made  by  a  croto 
(lose  by. 


448 


LIGHI. 


PIG.  15. 


A 


JiCtAB,  a  man  on  a  distant  mountain,  or  spire,  and  CD  a  tiow 
dose  oy. 

The  man  will  appear  only  as  high  as  the  line  C  D,  which  is  tne  heigh* 
of  the  crow. 


Q.  Why  does  the  moon  appear  to  us  so 
much  larger  than  the  stars,  though,  in  fact, 
it  is  a  great  deal  smaller  ? 

A.  Because  the  moon  is  very  much  nearer 
to  us  than  any  of  the  stars 


Let  A  B,  represent  a  fixed  star,  and  C  D,  the  moon, 

A  B,  though  much  the  larger  body,  will  appear  no  bigger  than  E  j 
whereas  the  moon  (C  D,)  will  appear  as  large  as  the  line  C  D,  to  tht 
9i)eclaU)r  G. 

The  moon  is  240,000  miles  from  the  earth,  not  quite  a  quarter  of  amiUhti 
of  miles.  The  nearest  fixed  stars  are  20,000,000,000,000,  (that  is  twenty 
billions.) 

If  a  ball  went  500  miles  an  hour,  it  would  reach  the  moon  in  twenty 
days  ;  but  it  would  not  reach  the  neare>;t  fixed  star  in  4,500,000  years.  Had 
it  begun,  therefore,  when  Adam  was  created,  it  would  be  no  further  on  ita 
journey  than  a  coach  (which  has  to  go  from  the  Land's  End,  Cornwail,  to 
the  Tiost  norllief  i  oa  ts  of  Scotland)  after  it  has  passed  about  three-qaar««'^ 
of  a  mile. 


1651. 


FIG.  16. 


B 


LIGHT. 


449 


1652. 

Q.  Why  does  the  moon  (which  is  a  sphere) 
appear  to  be  a  fiat  surface  ? 

A.  Because  it  is  so  far  o  f  that  we  cannot 
distinguish  any  difference  between  the 
\engt\  of  the  rays  issuing  from  the  edge  and 
those  which  issue  from  the  centre. 

FIG.  17. 

A 

c 

The  rays  A  D,  and  C  D,  appear  to  be  no  longer  than  the  ray  B  D ;  but 

if  all  the  rays  seem  of  the  same  length,  the  part  B,  will  not  seem  to  be 
nearer  to  us  than  A  and  C  ;  and  therefore,  ABC,  will  look  like  a  flat  or 
siraight  line. 

The  rays  A  D,  and  C  D,  are 240,000  miles  long. 

The  ray  B  D,  is  238,910  miles  long. 

1653 

Q.  Why  do  the  sun  and  stars  (which  are 
spheres)  appear  to  be  fiat  surfaces  ? 

A.  Because  they  are  at  such  an  immense 
distance,  that  we  can  discern  no  difference  of 
length  between  the  rays  which  issue  from 
the  edge  and  those  which  issue  from  the 
centre  of  these  bodies. 

The  rays  A  D,  and  C  D,  appear  no  longer  than  B  D  ;  and  as  B  appeari 
to  be  no  nearer  than  A  or  C,  therefore,  A,  B,  C,  must  all  seem  equally  dis- 
tant ;  and  ABC,  will  seem  a  flat  or  straight  line.    {See  Figure  17.) 

1654. 

Q.  Why  does  distance  make  an  object  in- 
mihle  ? 

A.  Because  no  visible  perpendicular  can 
v)e  inserted!  between  the  h'nes  which  form 
38* 


450  LIGHT. 

the  angle;  or  because  the  lines  actuall} 
cross  before  they  meet  our  eye. 

FIG.  18. 


Here  the  tree  A  D,  would  not  be  visible  to.the  spectator  C,  even  if  he 
were  to  approach  as  far  a<?  B  ;  becaiue  no  visible  perpendicular  can  be  in- 
eerted  between  the  two  lines  A  C,  D  C,  at  the  point  B,  and  after  B,  the 
lines  would  cross ;  therefore,  the  tree  would  be  invisible  from  C,  till  after 
the  spectator  had  passed  B. 

1655. 

Q.  What  is  the  meaning  of  perspective  ? 

A.  The  science  of  perspective  teaches  to 
draw  on  a  plain  surface  true  pictures  of  ob- 
jects as  they  appear  to  the  eije  from  any  dis- 
tance, and  in  any  position. 

"  Plain  surface,"  a  flat  or  even  surface.  The  word  perspective  is  from 
he  Latin  ^jer,  (through  ;)  and  specioj  (to  look.) 

1656. 

Q.  What  is  the  use  of  Telescopes  ? 
A.  They  gather  together  the  rays  of  light, 
imd  a  greater  quantity  are  brought  to  the  eye. 

1657. 

Q.  How  can  these  rays  be  gathered  to- 
gether? 

A.  Rays  of  light  diverge  ;  that  is,  spread 
out,  in  all  directions  from  a  luminous  ob- 
ject. The  number  of  these  diverging  rays 
which  will  enter  the  eye,  is  limited  by  the 
«ize  of  the  pupil.    But,  before  they  leach 


> 

LIGHT.  451 

the  eye,  they  may  be  received  upon  a  glass 
lens  of  a  convex  form,  which  will  have  the 
effect  of  collecting  them  into  a  space  less  in 
magnitude  than  the  pupil  of  the  eye.  If 
the  eye  be  placed  where  the  rays  are  thm 
collected,  all  the  light  will  enter  the  pupil 

1658. 

Q.  Why  do  telescopes  enable  us  to  see  ob- 
jects invisible  to  the  naked  eye  ? 

A.  Because  they  gather  together  more 
luminous  rays  from  obscure  objects  than  the 
eye  can ;  and  form  a  bright  image  of  them 
in  the  tube  of  the  telescope  where  they  are 
magnified. 

As  many  times  as  the  dimensions  of  the  ohjett-glass  exceed  the  dimen 
pions  of  the  pwpil  of  the  eye,  so  many  times  the  penetrating  powers  oi  me 
telescope  will  exceed  that  of  the  naked  eye. 

1659. 

Q.  When  a  ship  (out  at  sea)  is  approach- 
ing the  shore,  why  do  we  see  the  small  masts 
before  we  see  the  bulky  hull  ? 

A.  Because  the  earth  is  round ;  and  the 
curve  of  the  sea  hides  the  hull  from  our  eye»« 
after  the  tall  masts  have  become  visible. 


PIG.  19. 

 J^A 


Her  5,  ciily  that  part  of  the  ship  above  the  line  A  O,  can  bo  seen  bf  Ikd 
Ipectaior  A  ;  the  rest  of  the  ship  is  liidden  by  the  swell  of  the  curve  1)  fc 


152  LIGHT. 


1660. 

Q.  Horn  is  transparent ;  why  are  not  horr. 
shavings  transparent  also  ? 

A.  Because  the  surface  of  the  shaving 
has  been  torn  and  rendered  rough;  and  the 
rays  of  h'ght  are  too  much  reflected  and  re- 
fraded  by  the  rough  surflice  to  be  trans- 
mitted through  the  shaving,  so  as  to  pro- 
duce transparency. 

1661. 

Q.  Why  does  wetting  a  cornelian  make  it 
more  transparent  ? 

A.  Because  the  pores  of  the  cornelian  are 
then  filled  with  water  ;  and  as  the  density  of 
the  mass  is  rendered  somewhat  more  uni- 
form than  when  those  pores  were  filled  with 
air,  the  stone  becomes  more  transparent. 

Transparency  depends  on  the  uniformity  of  the  parts. 

If  the  parts  of  any  substance  are  not  pretty  uniform,  the  rays  of  light  are 
refracted  and  absorbed  so  frequently,  that  no  part  of  them  can  emerge  on 
the  opposite  side. 


SECTION  I.  THE  EYE,  THE  SEAT  OP  VISION, 

1662. 

Q.  What  is  meant  by  the  retina  of  the 
eye  V 

A.  The  net  work,  which  lines  the  hach 
of  the  eye,  is  called  the  retina. 


THE  EYE,  THE  SEAT  OF  VISION. 


453 


PIG.  20. 


The  net-work  A  B  C,  is  called  the  retina,  and  the 
projecting  part  D  E  F,  is  called  the  cornea. 

N.  B.  This  net-work  is  composed  of  a  spreit*J'»t!f 
out  of  the  fibres  of  the  nerve  of  vision. 


1663. 

Q  Does  light  admitted  through  the  pu- 
pil to  the  retina  produce  vision  ? 

A.  Yes ;  provided  the  light  enter  in  suf- 
ficient quantity. 

1664. 

Q.  What  is  that  portion  of  the  eye  called 
which  in  some  persons  is  blue,  in  others  gray 
or  hazel  ? 

A.  It  is  called  the  iris. 

1665. 

Q.  In  the  centre  of  the  iris  is  a  circulai 
Uack  spot,  what  is  this  called  ? 

A.  It  is  called  the  pupiL  But  this  spot 
is  not  a  black  substance  but  an  aperture^ 
which  appears  black  only  because  the  cham- 
ber within  it  is  dark.  It  is  properly  speal^- 
ing  the  window  of  the  eye,  through  which 
light  is  admitted,  which  strikes  on  the 
retina, 

1666 

Q.  Why  are  some  persons  near-sighted  ? 
A.  Because  the  cornea  of  their  eye  is  pti 


454  LIGHT. 

pmninerd,  that  the  image  of  distant  objecln 
is  formed  before  it  reaches  the  retina;  and, 
therefore,  is  not  distinctly  seen. 

1667. 

Q.  What  is  meant  by  the    cornea  of  the 

A.  All  the  outside  of  the  visible  part  of 
the  eye-ball. 

PIG.  21 

The  curve  A  B  C,  is  called  the  cornea. 

If  this  curve  be  too  prominent  (or  convex,)  tha 
eye  is  near-sighted. 

If  too  flat  (or  concave,)  the  eye  is  far-sighted. 
1668. 

Q.  What  sort  of  glasses  do  near-sighted 
persons  wear  ? 

A.  If  the  cornea  be  too  convex  (or  pro- 
jecting,) the  person  must  wear  double  con- 
cave  glasses,  to  counteract  it. 

1669. 

Q.  What  is  meant  by  "  double  concaiH 
f^lasses?^^ 

A,  Glasses  hollowed-in  on  both  sides. 

FIG.  22. 

I  ^        Figure  22  is  double  conca'"?,  or  conca^  e  on  boih  lides. 


THE  EYE,  THE  SEAT  OF  VISION. 


455 


1670. 

Q  Where  is  the  image  of  objects  formed, 
If  the  cornea  be  too  convex  ? 

A.  If  the  cornea  be  too  convex,  the  image 
of  a  distant  object  is  formed  in  the  vi- 
treous humors  of  the  eye,  and  not  on  the 
retina, 

PIG.  23. 

Thus  the  image  is  formed  at  D  E,  and  not  on  A  B 
C,  (the  retina.) 


1671. 

Q.  What  is  the  use  of  double  concave  spec- 
tacle glasses  ? 

A.  To  cast  the  image  further  hack,  in  order 
that  it  may  be  thrown  upon  the  retina  and 
b^^rome  visible  ? 

1672. 

Q.  Why  are  old  people  far-sighted  1 

A.  Because  the  humors  of  their  eyes  are 

dried  up  hy  age;  in  consequence  of  which. 

the  cornea  sinks  in,  or  becomes  flattened. 

1673. 

Q.  Wliy  does  the  flattening  of  the  cornea 
prevent  persons  seeing  objects  which  are 
near? 

A.  Because  the  cornea  is  too  flat,  and  the 
image  of  near  objects  is  not  completely 


45  G  LIGHT. 

formed,  when  their  rays  reach  the  retina;  in 
consequence  of  which,  the  image  is  imper- 
fect and  confused. 

FIG.  24. 

The  perfect  image  is  made  at  D  E ;  and  not  on 
ABC,  (the  retina.) 


1674. 

Q.  What  sort  of  glasses  do  old  people 
wear  ? 

A.  As  their  cornea  is  not  sufficiently  con- 
vex, they  must  use  double  convex  glasses,  to 
enable  them  to  see  objects  near  at  hand. 

1675. 

Q.  What  sort  of  glasses  are  ''double  con- 
vex spectacle-glasses  ? ' ' 

A.  Glasses  which  curve  outwards  on  hc*^ 
sides. 

FIG.  25. 

I    I        Figure  25  is  double  convex,  or  convex  on  both  sides. 


1676. 

Q.  What  is  the  use  of  double  convex  spec- 
tacle glasses  ? 

A.  To  shorten  the  focus  of  the  eye,  and 
bring  the  image  of  distant  objects  upon  the 
retina. 


THE  EYE,  THE  SEAT  OF  VISION. 


457 


1677. 

Q.  Why  do  near-sighted  persons  bring  ob- 
jects close  to  the  eye,  in  order  to  see  them  ? 

A.  Because  the  distance  between  the 
front  and  hack  of  the  eye  is  so  great,  that  the 
image  of  distant  objects  is  formed  in  front 
of  the  retina  ;  but  when  objects  are  brough  t 
near  to  the  eye^  their  image  is  thrown  fur- 
ther hack,  and  made  to  fall  on  the  retina. 

1678. 

Q.  Why  do  old  people  hold  objects  far  off, 
in  order  to  see  them  better  ? 

A.  Because  the  distance  between  the 
front  and  hack  of  their  eyes  is  not  great  enough; 
when,  however,  objects  are  held  further  off, 
it  compensates  for  this  defect ;  and  a  per- 
fect image  is  formed  on  the  retina. 

1679. 

Q.  Why  are  hawks  able  to  see  such  an 
immense  way  off? 

A.  Because  they  have  a  muscle  in  the 
eye,  which  enables  them  to  fi^atten  their  cor 
nea,  by  drawing  back  the  crystalline  lens. 
{Seefig^  21.) 

This  muscle  is  called  the  Marsupium. 
1680. 

Q.  Why  can  hawks  see  objects  within 
half  an  inch  of  their  eye,  as  well  as  those 
a  long  way  off? 

39 


458 


LIGHT. 


A.  Because  their  eyes  are  furnished  with 
a  flexible  bony  rim,  which  throws  the  cor- 
nea forward y  and  makes  the  hawk  near- 
sigJttcd. 

SECTION  ir  DECEPTIONS  OF  VISION. 

1681. 

Q.  Why  cannot  we  count  the  posts  of  a 
fence,  when  we  are  riding  rapidly  in  a  rail- 
road car  ? 

A.  Because  the  light  from  each  post  falls 
upon  the  eye  in  such  rapid  succession,  that 
the  vibration  continues  for  a  certain  time  ; 
just  as  the  string  of  a  bow  vibrates  after  it 
has  been  struck,  so  the  vibration  of  the  re- 
tina, after  the  object  has  been  withdrawn 
produces  a  perception  of  its  presence. 

1682. 

Q.  How  can  the  apparent  magnitude  of 
the  sun,  at  the  time  of  his  rising,  and  again 
at  noon-day,  be  measured  ? 

A.  This  may  be  accomplished  by  extend- 
ing two  threads  of  fine  silk,  fastened  in  a 
fram3,  parallel  to  each  other.  The  frame 
should  be  placed  in  such  a  position,  and  at 
such  a  distance  from  the  eye,  that  when 
presented  to  the  sun  or  moon  in  the  horizon, 
the  threads  will  exactly  touch  its  upper  and 


DECEPTIOJ^^S  OF  VISION. 


459 


lower  limb,  or  in  other  words,  be  just  Buf- 
iciently  separated  to  admit  of  the  disc  of 
the  smi  or  moon  to  appear  between  th3n> 
and  touch. 

Now,  if  the  sun  or  moon  be  viewed  in  the 
same  manner  at  noon-day,  it  will  be  found 
that  they  are  just  far  enough  apart  to  ad- 
mit of  the  disc  between  them,  showing  that 
the  apparent  increased  magnitude  at  rising 
and  setting,  is  an  optical  deception,  or  ror 
ther,  an  error  in  judgment. 

1683. 

Q.  Can  you  relate  how  Captain  Score^hy, 
when  navigating  the  Greenland  Se2/«,  L<aw 
a  ship  at  a  great  distance  below  the  horizon  ? 

A.  He  saw  the  inverted  image  of  a  ship 
in  the  air,  although  it  was  heloiv  the  ho  izon, 
and  on  observing  it  attentively,  he  dlsoo- 
vered  it  to  be  his  father's  ship  FamG.  which 
at  that  moment  was  seventeen  miles  bemv  tlu 
horizon,  and  thirty  miles  distant. 

16S4. 

Q.  How  can  you  account  for  the  inverted 
image  of  the  ship — why  did  he  not  ^"ee  it 
in  its  proper  position,  with  its  hull  next  the 
water  ? 

A.  In  this  instance  the  stratum  of  air 
nt^arest  the  earth's  surface  was  Icsv'  dense 


460 


LIGHT. 


than  that  immediately  above  it,  and  there- 
fore, the  refractive  power  of  the  uppei 
•stratum  was  greater  than  the  lower. 

1685. 

Q.  If  you  move  a  stick  (burnt  at  one  end) 
pretty  briskly  around,  it  seems  to  make  a 
circle  of  fire — ^why  is  this  ? 

A.  Because  the  eye  retains  the  image  of 
any  bright  object,  after  the  object  itself  is 
withdrawn;  and  as  the  spark  of  the  stick 
returns  before  the  image  has  faded  from  the 
eye,  it  seems  to  form  a  complete  circle. 

The  light  proceeding  from  the  stick  en- 
ters the  eye,  and  causes  certain  vibrations, 
which  are  so  exceedingly  rapid,  that  the  ac- 
tion of  the  light  is  not  retarded  for  a  suffi- 
cient length  of  time  to  perceive  the  motion 
of  the  stick. 

1686. 

Q.  If  separate  figures  (as  a  man  and  a 
horse)  be  drawn  on  separate  sides  of  a  card, 
and  the  card  twisted  quickly,  the  man  will 
seem  to  be  seated  on  the  horse — why  is 
this? 

A,  Because  the  image  of  the  horse  re- 
mains upon  the  eye  till  the  man  appears. 

The  Thauraatrope  is  constructed  on  this  principle. 


REFRACTION. 


46] 


CHAP.  II.— REFKACTION 

1687. 

Q.  What  is  meant  by  refraction  ? 
A.  Bending  a  ray  of  light,  as  it  passes 
from  one  medium  to  another. 

1688. 

Q.  Does  air,  possess  the  \)vo]}QY\y  of  re* 
frading  light  ? 

A.  Yes;  the  more  dense  the  air,  the 
greater  is  its  refractive  power.  Conse- 
quently that  portion  of  the  atmosphere  at 
the  earth's  surface  possesses  the  greatest  re- 
fr active  power;  its  density  gradually  dimin- 
ishing according-  to  its  distance  from  the 
earth,  till  it  becomes  so  rare  as  scarcely  to 
produce  any  refraction  upon  light. 

1689. 

Q.  How  is  a  ray  of  light  lent,  as  it  passea 
from  one  medium  to  another? 

A.  When  a  ray  of  light  passes  into  a 
denser  medium  it  is  bent  toiuards  the  per- 
pendicular.   When  it  passes  into  a  rarer 
medrim  it  is  hent  from  the  perpendicular. 
89* 


462 


REFRACTION. 


PIG.  26.  FIG.  27. 


S  ippose  D  E,  to  be  a  perpendicular  line. 

If  A  B,  (a  ray  of  light)  enters  the  water,  it  will  be  bent  towards  il.a 
perpendicular  to  C. 

If  (on  the  other  hand)  C  B,  (a  ray  of  light)  emerges /rom  the  water,  it 
would  be  beut  away  from  the  perpendicular  towards  A. 

1690. 

Q.  Why  does  an  oar  in  water  appear 
bent? 

A,  Because  the  part  out  of  the  water  is 
seen  in  a  different  medium  to  the  part  in 
the  water ;  and  the  rays  of  these  two  parts, 
meeting  together  at  the  surface  of  the 
river,  form  an  angle — or  in  other  words, 
make  the  oar  look  as  if  it  were  bent. 

N.  B.  As  all  rays  of  light  are  refracted  (or  bent)  more  in  iheir  passaga 
through  water  ihaii  in  their  passage  through  air,  they  will  tend  to  crosg 
each  other  at  the  surface  of  the  water,  and,  of  course,  form  aa  elbow  or 
angle. 

1691. 

Q.  Why  does  a  spoon  (in  a  glass  of  wa- 
ter) always  appear  bent  ? 

A.  Because  the  light  (reflected  from  the 


REFRACTION.  463 

spoon)  is  refracted  as  it  emerges  from  the 
water. 

i^See  Fig.  27.)    The  spoon  ABC,  will  appear  beat,  like  A  B  D« 
1692. 

Q.  Why  does  a  river  always  appear  more 
shallow  than  it  really  is  ? 

A.  Because  the  light  of  the  bottom  of 
the  river  is  refracted^  as  it  emerges  out  of 
the  water. 

{See  Fig.  "21.)  The  bottom  of  the  river  will  appear  elevated  like  ihi 
bowl  of  the  spoon  D. 

1693. 

Q.  How  much  deeper  is  a  river  than  it 
seems  to  be  ? 

A.   About  one-third.    If,  therefore,  a 

river  seems  only  four  feet  deep,  it  is  really 
six  feet  deep. 

The  exact  apparent  depth  would  be  To  find  the  real  depth,  multi- 
ply by  4  and  divide  by  3— thus  4^X44-3=6,  real  depth. 

N.  B.  Many  boys  get  out  of  their  depth  in  bathing,  in  consequence  of 
this  deception.  Remembei',  a  river  is  alwayg  one-third  deeper  than  it  ap- 
pears to  be : — thus,  if  a  river  seems  to  be  4  feet  deep,  it  is  in  reality  nearly 
U  feet  deep,  and  so  on. 

1694. 

Q.  Why  do  fishes  seem  to  be  nearer  the 
surface  of  a  river  than  they  really  are  ? 

A.  Because  the  rays  of  light  from  th(3 
fish  are  refracted,  as  they  emerge  from  tlie 
eye  :  and  (as  a  bent  stick  is  not  so  far  from 
end  to  end,  as  a  straight  one)  so  the  fishes 
appear  nearer  to  our  eye  than  they  really 
are.    {See  Fig.  27.) 


464 


REFRACTION. 


1695. 

Q.  Into  how  many  parts  may  a  ray  of 
iight  be  divided  ? 

A.  Into  three  parts:  blue,  yellow,  and  red? 

N  B.  These  three  colors,  by  combination,  make  seven.  I. — R^d.  2  — 
Orange  (or  red  and  yellow.)  3. —  Yellow.  4. — Green  (f>r  yellow  and 
^ine.)  5.' 'Blue,  6. — Jnc//^o  (a  shade  of  blue  j)  and  7. —  Violet  (<>r  blue 
Uid  red.) 

1696. 

Q.  How  is  it  known,  that  a  ray  of  light 
consists  of  several  different  colors  ? 

A.  Because,  if  a  ray  of  light  be  cast 
upon  a  triangular  piece  of  glass  (called  a 
prism,)  it  will  be  distinctly  divided  into 
seven  colors:  1. — Red;  2. — Orange;  3. 
Yellow;  4. — Green;  5. — Blue;  6. — Indigo; 
and  7. — Violet. 

1697. 

Q.  Why  does  a  prism  divide  a  ray  of  light 
into  various  colors  ? 

A.  Because  all  these  coWPs'^ave  differ- 
ent refractive  susceptibilities.  Bed  is  re- 
fracted hasty  and  blue  the  most ;  therefore, 
the  blue  color  of  the  ray  will  be  bent  to  the 
top  of  the  prism,  and  the  red  will  remain  at 
llie  bottom. 


PIG.  28. 


B 


REFRACTION.  465 

Here  the  ray  A  B,  (received  on  a  prism  at  B,)  would  have  the  blue 
part  bent  up  to  C  ;  the  y^'ow  part  to  D;  and  the  red  part  no  further 
than  E. 

1698. 

Q.  What  is  meant  by  the  refraction  of  a 
ray? 

A.  Bending  it  from  its  straight  line. 

Thus  t).e  ray  A  B,  of  the  last  figure  is  refracted  at  B  into  three  couifi» 
C,  D,  and  E. 

1699. 

Q.  What  is  the  cause  of  a  rainbow  ? 

A.  When  the  clouds  opposite  the  sun  are 
very  dark,  and  rain  is  still  falling  from  them, 
the  rays  of  the  bright  sun  are  divided  by  the 
rain-drops,  as  they  would  be  by  a  prism. 

FIG.  29. 


Let  A,  B,  and  C,  be  three  drops  of  rain ;  S  A,  S  B,  and  S  C,  three  ray« 
of  the  sun.  8  A,  is  divided  into  three  colors;  the  blue  and  yellow  ura 
bent  above  the  eye  D,  and  the  red  enters  it. 

The  ray  S  B,  is  divided  into  the  three  colors  ;  the  blue  is  bent  above  t>.« 
eye,  and  the  red  falls  below  the  eyeD  ;  but  the  yellow  enters  it. 

The  ray  S  C,  is  also  divided  into  the  three  olors.  The  b'ue  (whicJi  h 
bent  most)  enters  the  eye  ;  and  the  other  two       below  it.    Thuy  f»y« 


466 


REFRACTION  > 


eees  the  Llae  of  C  and  of  all  drops  in  the  posit>on  of  C  ;  the  yellow  of  b 
and  of  all  drops  in  the  position  of  B  ;  and  the  red  of  A,  and  of  all  dropf 
in  the  position  of  A  j  and  thus  it  sees  a  rainbow. 

1700. 

Q.  Does  every  person  see  the  same  colors 
from  the  same  drops  ? 

A,  No ;  no  two  persons  see  the  same  rain 
hoto. 

To  another  spectator,  the  rays  from  S  B,  might  be  red  instead  of  yel- 
low; the  ray  from  S  C,  yellow ;  and  the  blue  might  be  reflected  from 
Bome  drop  below  C.  To  a  third  person,  the  red  msy  issue  from  a  drop 
above  A,  and  then  A  would  reflect  the  yellow,  and  B  the  blue,  and  so  on. 

1701. 

Q.  Why  are  there  often  two  rainbows  at 
one  and  the  same  time  ? 

A.  In  one  rainbow  we  see  the  rays  of 
the  sun  entering  the  rain  drops  at  the  top, 
and  reflected  to  the  eye  from  the  bottom. 

In  the  other  rainbow,  we  see  the  rays  of 
the  sun  entering  the  rain  drops  at  the  bot- 
fom^  and  reflected  to  the  top,  whence  th(^y 
reach  the  eye 

FIG.  30. 


REFRACTION. 


467 


Here  the  lay  S  A,  (of  the  primary  rainbow)  strikes  the  drop  at  A — ia 
tefracted  or  bent  to  is  then  reflected  to  C,  where  A  is  refracted  again, 
Kiid  reaches  the  eye  of  the  spectator.   {See  below.) 


Here  the  ray  of  S  B,  (of  the  secondary  rainbow)  strikes  the  tfrop  at  B 
-is refracted  to  A — is  then  reflected  to  C — is  again  reflected  to  D,  wlien 
t  is  again  refracted  or  bent  till  it  reaches  the  eye  of  the  spectator. 


Q.  Why  are  the  colors  of  the  second  bow 
all  reversed  ? 

A.  Because  in  one  bow  we  see  the  rays, 
which  enter  at  the  top  of  the  rain-drops, 
refracted  from  the  bottom : 

But  in  the  other  bow  we  see  the  rays 
which  enter  at  the  bottom  of  the  rain-ciroj^s 
Rafter  two  reflections,)  refracted  from  the  top. 


(See  Figure  32.)   Here  A  B  C,  represent  three  drops  of  ram  in  Tci 

fcECONDARY  (or  Upper)  RAINBOW. 

The  least  refracted  line  is  red,  and  blue  the  most 

So  the  RED  (or  least  refracted  rays)  of  all  the  drops  in  the  ]iosiii,:n  of  A 
— the  YELLOW  of  those  iii  the  position  of  B — and  the  blue  (or  the  most  to* 
fracted  rays)  of  the  lowest  drops,  all  meet  the  ey?  D,  and  form  s  iB\n 
bow  to  the  spectator. 

The  reason  why  the  primary  bow  exhibits  the  stronger  colors  i«  tb.J»-« 
)ecan?e  the  col' rs  are  se-»n  after  "'-tc.  reflection  and  <Wo  r.ffraetlone  ;  h\JS 


PIG.  31. 


1702. 


468 


EBFRACTION. 


FIG.  32. 


if;  // 


the  colors  of  the  secondary  (or  upper)  rainbow,  undergo  two  refleetloiv 

and  two  refractions. 

{See  Figure  31.)  Here  also  the  least  refracted  ray  is  red,  and  the  mo$t 
refracted  bltte  (as  in  the  former  case;)  but  the  position  of  each  is  re* 
versed. 

1703. 

Q.  Why  does  a  soap  bubble  exhibit  such  a 
varietTj  of  colors  ? 

A.  Because  the  thickness  of  the  film  through 
(vhich  the  rays  pass,  is  constantly  varying. 

1704. 

Q.  How  does  the  thickness  of  the  film  af- 
fect the  color  of  the  soap  bubble  ? 

A.  Because  different  degrees  of  thickness 
in  the  film  produce  different  powers  of  re^ 
fraction;  and,  therefore,  as  the  thickness  of 
the  film  varies,  different  colors  reach  tho 
eye. 


REFRACTION. 


469 


1705. 

Q.  Why  is  a  soap  bubble  so  constantly 
changing  its  thickness  ? 

A.  Because  the  water  runs  down  from  th 
top  to  the  bottom  of  the  bubble,  till  th^ 
crown  becomes  so  thin  as  to  burst. 

1706. 

Q.  Why  are  the  late  evening  clouds  red  ? 
A.  Because  red  rays,  being  the  least  r»» 
frangible^  are  the  last  to  disappear. 

FIG.  33. 


Suppose  P  A,  to  be  a  red  ray,  P  B,  yellow,  and  P  C,  blue— if  the  carta 
tdrns  in  the  direction  of  C  B  D,  it  is  quite  manifest  that  a  spectator  stand- 
at  C,  or  B,  (carried  round  in  the  same  direction,)  would  lose  sight  of 
toe  red  rays  (A.)  last  of  all. 

1707. 

Q.  Why  are  the  early  morning  clouds  red} 
A,  Because  red  rays  being  the  least  re* 
frangible  are  the  first  to  appear- 
40 


470 


REFRACTION. 


{See  Figure  33.)  We  must  suppose  the  sun  to  be  on  Uhe  left  side  of  tn# 
diagram— or  (what  will  answer  the  same  purpose)  suppose  the  earth  to  be 
turning  in  the  direction  of  D  A  P,  then  it  is  quite  clear,  that  every  person 
on  the  earth's  surface  will  pass  under  A,  (the  red  rays)  before  he  passet 
ander  B,  Dr  C.  (and  therefore,  his  early  morning  rays  will  be  red.) 

1708. 

Q.  Why  does  the  sun  look  red  in  a  fog  ? 

A.  Because  red  rays  have  a  greater  mo- 
mentum  than  any  other  rays ;  and  this  supe- 
rior momentum  enables  them  to  penetrate 
the  dense  atmosphere  more  readily  than 
either  blue  or  yellow  rays^  which  are  either 
absorbed  or  reflected  by  the  fog. 

1709. 

Q.  Why  are  the  edges  of  clouds  more 
luminous  than  their  centres  ? 

A.  Because  the  body  of  vapor  is  thinnest 
at  the  edges  of  the  clouds  ? 

1710. 

Q.  What  is  the  cause  of  morning  and 
evening  twilight  ? 

A.  When  the  sun  is  below  the  horizon, 
Ihe  rays  which  strike  upon  the  atmosphere 
or  clouds  are  bent  down  towards  the  earthy  and 
produce  a  little  light  called  twiUght. 

{See  Figure  33.)    Here  the  rays  of  P  A,  will  give  some  light. 
1711. 

Q.  Sometimes  ships  are  distinctly  seen  by 
an  observer  on  shore^  before  they  are  actu- 
ally  above  the  horizon — explain  this? 


REFRACTION. 


A.  This  is  owing  to  the  refracting  power 
of  the  atmosphere  at  the  time.  The  difFer- 
(mt  strata  of  air  being  of  unequal  density^ 
tlie  rays  of  light  from  the  ship  to  the  eye 
of  the  observer,  are  bent  in  3s  curve;  so  that 
Ihe  vessel  is  visible  before  it  is  really  above 
the  horizon. 

It  is  owing  to  this  refracting  power  of  the  atmosphere  that  the  sun  ajv- 
pears  to  us  before  he  rises,  and  we  see  hira  after  he  has  actually  set. 

1712. 

Q.  Why  does  mother  of  pearl  show  so  many 
colors  ? 

A.  Mother  of  pearl  consists  of  a  vast  num- 
ber of  very  thin  half-transparent  layers  of 
unequal  thickness,  overlapping  each  other 
like  the  scales  of  a  fish. 

Where  these  layers  terminate,  are  very 
small  grooves  or  streaks  running  in  all  di- 
rections,  which  act  like  prisms. 

It  is  these  streakings^  or  grooves,  which 
cause  the  various  and  changing  colors  of 
mother  of  pearl. 

The  same  thing  may  very  easily  be  imitated,  and  iS  frequently  d»m8  i( 
what  are  called  "  iris  ornaments,"  first  invented  by  John  Barton,  Esq  oi 
the  Royal  Mint,  England.  These  iris  ornaments  are  made  of  steel,  a  id 
have  about  30,000  grooves  per  inch;  they  are  used  in  court  dresses,  lof 
buttons,  sword-handles,  etc.,  and  are  very  brilliant  indeed. 

Mother  of  pearl  may  also  be  imitated,  by  taking  impressions  of  i  rinwax, 
balsam  of  tolii,  isinglass,  or  gum;  these  impressions  will  exhibit  all  the 
shades  and  colors  of  mother  of  pearl,  merely  because  the  impression  will 
De  streaked  or  grooved  in  a  similar  way. 

1713. 

Q.  Why  do  stars  twinkle  more  than 
usual  just  previous  to  a  rain  ? 


472 


REFRACTION. 


A.  Because  the  air  is  unequally  filled  witb 
vapor ^  which  offers  constant  and  unequal  oh 
dructions  to  the  passage  of  the  rays  of  light 

1714. 

Q.  Why  are  some  things  transparent  ? 

A.  Because  every  part  between  the  two 
surfaces  has  a  uniform  refracting  power,  or 
(in  other  words)  has  in  every  place  the  same 
density. 

And,  therefore,  the  rays  of  light  emerge  on  the  opposite  side. 
1715. 

Q,  Why  are  some  things  not  transparent? 

A.  Because  the  particles  which  compose 
them  are  separated  by  minute  joom  or  spaces ^ 
which  have  a  different  density  from  the 
particles  themselves. 

Therefore,  the  rays  of  light  are  reflected  and  refracted  loo  often  to 
emerge. 

1716. 

Q.  Why  are  dry  paper  and  calico  (which 
are  opaque)  made  transparent  by  being  oiled? 

A.  Because  the  pores  are  filled  by  the 
oil,  which  has  nearly  the  same  density  as 
the  substance  of  the  paper  itself — by  which 
means  a  uniform  density  is  effected,  and  the 
substance  becomes  transparent. 

1717. 

Q.  Why  is  glass  (which  is  trp.nsparent) 
rendered  opaque  by  being  ground  or  pulve- 
rized ? 


REFLECTION. 


d73 


A.  Because  the  whole  substance  from 
surface  to  surface  is  no  longer  of  one  uni- 
form density. 

1718. 

Q  Why  do  the  stars  twinkle  7 

A.  Because  the  inequalities  and  undula- 
tions in  the  atmosphere  produce  unequal 
refractions  of  light;  and  these  unequal  re- 
fractions cause  the  twinkling  or  irregular 
brilliancy  of  the  stars. 


CHAP.  III.— REFLECTION 

1719. 

Q.  What  is  meant  by  reflection  of  light  ? 

A.  Reflection  in  optics,  means  the  re 
bounding  of  light  from  the  surfaces  on  which 
it  falls. 

1720. 

Q.  An  object  in  the  shade  is  not  so  bright 
and  apparent,  as  an  object  in  the  sun — why 
is  it  not  ? 

A.  Because  objects  in  the  shade  are  seen 
by  reflected  light  reflected,  that  is,  the  light  is 
twice  reflected  ;  and,  as  the  rays  of  light  are 
always  absorbed  in  some  measure  by  every 
substance  on  which  they  fall,  therefore, 
«ome  light  is  lost :  1st. — Before  the  second 
40* 


474 


REFLECTION. 


reflection  is  made ;  and  2nd. — ^In  the  object 
that  makes  the  second  reflection. 

Part  of  the  rays  are  absorbed,  and  part  are  scattered  in  al\  directions  by 
irregular  refleciions ;  so  that  rarely  more  than  half  is  reflected,  even,  from 
the  most  polished  metals. 

1721. 

Q.  Why  is  it  light  when  the  sky  is 
ijovered  with  thick  clouds  ? 

A.  Because  the  multiplied  reflections  of 
the  sun  in  the  atmosphere  are  sufficient  to 
give  light  upon  the  earth,  even  when  thick 
clouds  are  passing  over  the  disc  of  the  sun. 

1722. 

Q.  If  a  picture  be  highly  varnished,  or 
covered  with  a  glass,  it  cannot  be  seen  in 
certain  positions — why  not  ? 

A.  1st. — Because  the  glass  or  varnish  is 
a  reflector ;  and,  whenever  a  strong  light  is 
reflected  from  the  glass  to  the  eye  of  the 
spectator,  the  glass  or  varnish  becomes  very 
luminous,  and  the  picture  remains  in  com- 
parative darkness ;  and 

2nd. — When  the  spectator  is  so  placed, 
as  to  catch  the  rays  of  light  reflected  from 
the  glass  or  varnish,  his  eye  is  dazzled  and 
cannot  see  the  more  faintly  illuminated 
picture. 

1723. 

Q.  Why  do  you  see  the  reflection  ot  twa 
jAw&X^s,  or  two  fires,  in  a  looking-glass,  or 


REFLECTION. 


475 


window-pane,  though  there  be  only  om  cau- 
dle or  fire  in  the  room  ? 

A  Because  each  surface  of  the  looking* 
£;lass,  or  window-pane  makes  a  reflection. 

N.  B.  In  order  to  get  these  two  reflections,  vou  must  not  stand  dirccllj* 
be'ore  the  glass,  but  a  little  on  one  side. 

1724. 

Q.  Why  is  the  shadow  of  the  vtoon 
stronger  than  the  shadow  of  the  sun  ? 

A.  Because  the  light  of  the  moon  is  not 
BO  strong  as  the  light  of  the  sun ;  in  conse- 
quence of  which,  the  dispersed  and  reflected 
rays  of  the  moon  cannot  reduce  the  opacity 
of  shadow  so  much,  as  the  more  intense  raj^s 
of  dispersed  and  reflected  day-light. 

"  The  opacity  of  shadows,"  that  is,  the  darkness  of  shadows. 
1725. 

Q.  Why  is  an  ink  spot  on  linen  black  when 
first  made  ? 

A.  Because  the  ink  produces  a  chemical 
change  in  the  internal  condition  of  the 
fibres  of  the  linen,  by  which  it  loses  its  power 
of  reflecting  light;  and,  as  it  absorbs  the  rays 
of  the  sun,  the  spot  seems  black. 

The  hlacJc  color  of  ink  is  composed  of  a  compound  of  Tannic  acid,  sesqui 
*  oxide  of  iron,  and  water. 

1726. 

Q.  Wliy  does  the  black  ink-spot  on  linen 
turn  yellow  after  a  few  days  ? 


476 


REFLECTION, 


A.  Because  the  compound,  which  com 
poses  the  blackness  of  ink,  is  destroyed  by 
exposure  to  air ;  and  the  linen  partially  re- 
covers its  j)ower  of  reflecting  colors,  but  witli 
a  preference  to  yellow  rays. 

The  tannic  acid  and  water  are  in  a  measure  taken  up  by  the  air,  and  tii« 
•xiJe  of  iron  eaves  a  yellow  iron  mould  behind. 

1727. 

Q.  What  surfaces  reflect  light  best  ? 
A.  Smooth  and  polished  surfaces  are  the 
best  reflectors  of  light. 

1728. 

Q.  Glctss  is  a  smooth  polished  surface,  is 
it  a  good  reflector  of  light  ? 

A.  Glass  is  transparent ;  and  therefore, 
transmits  light;  but  if  one  of  its  surfaces  be 
covered  with  amalgam,  the  light  cannot 
pass  through  it,  and  is  consequently  reflected. 

1729. 

Q.  Why  are  some  things  shining^  and  others 
dull? 

A.  Because  some  things  reflect  rays,  and 
are  bright;  but  others  absorb  them, 

1730. 

Q.  Why  do  deserts  dazzle  from  sunshine  ? 
A.  Because  each  grain  of  sand  reflects  th€ 
rays  of  the  sun  like  a  mirror. 


COLOR. 


477 


CHAP.  IV.— COLOR. 

1731. 

Q.  Why  is  a  ray  of  light  composed  of  mi* 
lions  colors  ? 

A.  To  vary  the  color  of  different  objectg 
If  solar  light  were  of  one  color  onlVy  all  ob* 
jects  would  appear  of  that  one  color,  or  else 
black. 

1732. 

Q.  Some  things  are  of  one  color,  and  some 
of  another — explain  the  cause  of  this  ? 

A.  As  every  ray  of  light  is  compo^^ed  of 
all  the  colors  of  the  rainbow;  some  thmgs 
reflect  one  of  these  colors  and  some  another. 

1733. 

Q.  Why  do  some  things  reflect  one  color, 
and  some  another  ? 

A.  Because  the  surface  of  things  is  so 
differently  constructed,  both  physically  and 
chemically. 

1734. 

Q.  Why  is  a  rose  red  ? 

A.  Because  the  surface  of  a  rose  absorbs 
the  blue  and  yellow  rays  of  light,  and  reflects 
only  the  red. 

1735. 

Q.  Why  is  a  violet  blue  ? 

A.  Because  the  surface  of  the  violet  ah 


478  COLOR. 

sorbs  the  red  and  yellow  rays  of  the  san,  and 
reflects  the  blue  only. 

1736. 

Q.  Why  is  a  primrose  yellow  ? 

A.  Because  the  surface  of  the  primrose 
absorbs  the  blue  and  red  rays  of  solar  light, 
and  refl^ects  the  yellow. 

The  chief  reason  why  some  rays  are  absorbed  and  others  reflected  is,  be- 
cause ihe  corpuscles  which  compose  the  colored  substance  vary  in  magni- 
tude: — thus,  for  example,  if  the  diameter  of  a  corpuscle  of  equal  density 
with  air  be  twenly-one  millionth  of  an  inch,  it  will  reflect  purple  ;  if,  on 
the  other  hand,  it  be  twenty-nine  millionth  of  an  inch,  it  will  reflect  red, 
Bnd  &o  on. 

1737. 

Q.  Why  are  some  things  black  ? 
A.  Because  they  absorbs  all  the  rays  of 
light  and  reS^ect  none. 

1738. 

Q.  Wliy  are  some  things  white  ? 
A.  Because  they  absorb  none  of  the  rays 
of  light,  but  reflect  them  all. 

1739. 

Q.  Why  is  coal  black  ? 
A.  Because  it  absorbs  all  the  rays  of  Ihi 
sun  which  impinge  upon  it. 

1740, 

Q.  Why  are  froth,  and  spray,  and  many 
douds,  white? 

A.  Because  they  consist  of  an  infinite 
number  of  small  bubbles  or  vesicles,  which 


COLOR. 


479 


ftct  liKe  prisms  in  dividing  the  rays  of  light ; 
which,  by  uniting  again  before  they  meet 
the  eye,  give  the  appearance  of  white. 

1741. 

Q.  Why  are  snow,  sugar,  and  sdt  white  ? 
A.  {See  Q.  1738.) 

N.  B.  The  combination  of  all  colors  makes  white, 
1742. 

Q.  Why  are  the  leaves  of  plants  green  ? 

A.  Because  a  peculiar  chemical  principle, 
called  chlorophyll,  is  formed  within  their 
cells  ;  which  has  the  property  of  absorbing 
the  red  rays  and  of  reflecting  the  blue  and 
yellow ;  which  mixture  produces  green. 

Chlorophyll  (xKoipov  (pvWov^  chloron  phuUon,  a  green  leaf)  is  the  green 
matter  of  vegetable  substances. 

1743. 

Q.  Why  are  leaves  a  light  green  in  spring? 
A.  Because  the  chlorophyll  is  not  fully 
formed. 

1744. 

Q.  Why  do  leaves  turn  brown  in  autumn? 
A.   Because  the  chlorophyll  undergoes 
decar  and  is  not  replaced  as  it  is  in  spring. 

1745. 

Q.  Why  do  the  lustres  of  a  chandelier  seem 
tmted  with  various  brilliant  colors  ? 

A.  Because  each  ^^drop"  of  the  chande- 
lier is  so  cut  as  to  act  like  a  prism.    It  de- 


480 


COLOR. 


compom  the  light,  and  reflects  the  different 
ra.ys  thereof,  from  its  different  points  or 
angles. 

1746. 

Q.  Why  do  all  things  appear  black  in  tho 
dark  ? 

A.  In  the  dark  there  is  no  color,  because 
there  is  no  light  to  be  absorbed  or  reflected 
—and  therefore,  none  to  be  decomposed. 

"  Colors  are  but  phantoms  of  the  day, 

With  that  they're  born,  with  that  they  fade  away, 

Like  beauty's  charms,  tliey  but  amuse  the  sight, 

Dark  in  themselves,  till  by  reflection  bright, 

With  the  sun's  aid,  to  rival  him  they  boast, 

But  light  withdrawn,  in  their  own  shades  are  lost." 

Of  course,  in  certain  degrees  of  darkness,  all  objects  are  actually  tiwjtat 
ble.  The  question  refers  to  that  peculiar  degree  of  darkness,  when  the 
forms  of  objects  may  be  seen,  but  not  their  hues, 

1747. 

Q.  Why  is  the  sky  blue  on  a  fine  day,  and 
not  red  or  orange  ? 

A.  Because  the  momentum  of  red  and 
orange  rays  (being  greater  than  that  of 
blue)  causes  them  to  penetrate  beyond  the 
clouds ;  but  the  blue  rays  are  stopped  on 
their  passage  and  reflected. 

1748. 

Q.  Why  does  a  blue  dress  appear  green  by 
mndle  light  7 

A.  Because  the  light  of  a  candle* is  tinged 
with  yelhw  ;  and  this  yellow  tinge,  mixing 


COLOR. 


481 


with  the  blue  color  of  the  dress,  produces 
green . 

1749. 

Q.  Why  are  some  plants  white,  which  are 
k  5pt  in  the  dark  ? 

A  Because  chlorophyll  can  be  formed 
only  by  the  agency  of  the  sun's  rays ; 
and  it  is  this  peculiar  chemical  principle, 
which  gives  the  green  tinge  to  healthy 
leaves  and  plants. 

Some  plants  are  a  yellowish  green  from  the  same  cause. 
1750. 

Q.  Why  does  the  sun  most  generally  fade 
artificial  colors  ? 

A.  Generally,  the  loss  of  color  arises  from 
the  oxidation  of  the  substances  used  in  dye 
ing ;  as  tarnish  and  rust  are  an  oxidation 
of  metals. 

Sometimes,  however,  the  ingredients  of 
the  dye  are  otherwise  decomposed  by  the 
sun ;  and  the  color  (which  is  due  to  a  com- 
bination of  ingredients)  undergoes  a  change, 
ai5  soon  as  the  sun  deranges  or  destroys  that 
combination. 

1751. 

Q.  If  we  look  at  a  red-hot  fire  for  a  few 
minutes,  why  does  every  thing  seem  tinged 
with  a  bluish  green  color  ? 
41 


482 


COLOR. 


A.  Because  bluish  green  is  the  ''accidenlai 
color  of  red ;  and  if  we  fix  our  eye  upoK 
any  color  whatsoever,  we  see  every  object 
tinged  with  its  accident d  color  when  we  turn 
aside. 


The  accidental  color  is  the  color  which  would  be  required  to  be  addjd. 
1)  order  to  make  up  ivhite  light. 

The  accidental  color  of  red  is  bluish  green. 


Q.  Why  does  the  eye  perceive  the  acci- 
dental color  when  the  fundamental  one  is  re- 
moved ? 

A.  Because  the  nerve  of  the  eye  has  be- 
come tired  of  the  one,  but  still  remains 
fresh  for  the  perception  of  the  other. 

1753. 

Q.  If  we  wxar  blue  glasses^  why  does 
every  thing  appear  tinged  with  orange  when 
we  take  them  off? 

A.  Because  orange  is  the    accidental  color 
of  blue  ;  and  if  we  look  through  blue  glasses, 
we  shall  see  its  ''accidental  color when  we 
lay  our  glasses  aside. 


Q.  If  we  look  at  the  sun  for  a  few  ra.'> 


orange  is  blue, 
yellow  is  indigo, 
green  is  reddish  violet, 
blue  is  orange  red. 
indigo  is  orange  yellow, 
violet  is  yellow  green, 
black  is  white, 
white  is  black. 


1752. 


1754. 


COLOR. 


483 


ments,  every  thing  seems  tinged  with  a 
violet  c  jlor — why  is  this  ? 

A.  Because  violet  is  the  ''accidental  color" 
of  yellow;  and,  as  the  sun  is  yellow,  we  shall 
see  its  ''accidental  color"  violet  when  we 
turn  from  gazing  at  it. 

1755. 

Q.  Does  not  the  dark  shadow  (which  seems 
to  hang  over  every  thing  after  we  turn  from 
looking  at  the  sun)  arise  from  our  eyes  be- 
ing dazzled  ? 

A.  Partly  so ;  the  pupil  of  the  eye  is  very 
much  contracted  by  the  brilliant  light  of  the 
sun,  and  does  not  adjust  itself  immediately 
to  the  feebler  light  of  terrestrial  objects ; 
but,  independent  of  this,  the  '^accidental 
color of  the  sun  being  dark  violet,  would 
tend  to  throw  a  shadow  upon  all  things. 
{See  Q.  1751.) 

1756, 

Q.  ^Vhy  does  every  thing  seem  shadowed 
with  a  black  mist  when  we  take  off  our  com- 
mon  spectacles  ? 

A.  Because  the  glasses  are  white;  and 
black  being  its  "accidental  color,"  every 
thing  appears  in  a  black  shade  when  wo  lay 
our  glasses  down. 


COLOR. 


(The  law  of  an  accidjntal  color  is  this — Th«  accidental  color  is  alwayt 
half  the  g|  ectniin.  Thus,  if  we  take  half  the  iength  of  the  spectrum  by  a 
pair  of  compasses,  and  tii  one  leg  in  any  color,  the  other  leg  will  hit 
upon  its  accidental  color.) 

N.  B.  The  spectrum  means  the  Beven  colors  (red,  orange,  yellow,  green, 
blue^  indigo,  and  violet,)  divided  into  seven  eqital  bands,  and  placed  sido 
by  gide  in  the  order  just  mentioned. 

1757. 

Q.  Why  is  black  glass  foi'  spectacles  be^i 
for  wear  in  this  respect  ? 

A.  Because  white  is  the  accidental  color 
of  black  ;  and  if  we  wear  black  glasses,  eveiy 
thing  will  appear  in  white  light  when  we 
take  them  off. 

1758. 

Q.  Why  are  potatoes  wliich  grow  exposed 
to  the  air  and  light,  green  ? 

A.  Because  chlorophyll  is  formed  in  them 
under  the  influence  of  the  sun's  light. 


PART  VIL 

UHAP    I.— TRANSiVIISSION  OP  SOUND 

1759. 

Q,  How  IS  sound  produced  ? 

A.  The  vibration  of  some  sonorous  sub- 
Btance  produces  motion  in  the  air,  called 
sound-waves,  which  strike  upon  the  drum  of 
the  ear  and  give  the  sensation  of  sound. 

1760. 

Q.  How  fast  does  sound  travel  ? 
A.  About  13  miles  in  a  minute,  or  1142 
feet  in  a  second  of  time. 

Light  would  go  480  times  round  the  whole  earth,  while  sound  is  going 
13  miles. 

1761. 

Q.  Why  are  some  thinj^s  sonorous  and 
others  not  ? 

A.  The  sonorous  quality  of  any  substance 
depends  upon  its  hardness,  and  elasticity. 

1762. 

Q,  What  are  sonorous  bodies  ? 
A.  Bodies  which  produce  sound  are  called 
Bonorxis  bodies. 

41*  485 


486  TRANSMISSION  OF  SOUND. 

1763. 

Q.  What  kind  of  surfaces  are  best  adapted 
for  the  transmission  of  sound  ? 

A.  Smootli  surfaces,  such  as  ice,  water  oi 
hard  ground. 

1764. 

Q.  What  plan  do  savages  adopt  to  hear 
the  approach  of  an  enemy  or  beasts  of  prey? 

A.  They  place  their  ears  to  the  ground y 
and  by  this  means  can  distinguish  clearly 
the  approach  of  an  enemy, 

1765. 

Q.  Why  do  windows  rattle  when  carts  pas« 
by  a  house  ? 

A.  1st. — Because  glass  is  sonorous  ;  and 
the  air  communicates  its  vibrations  to  the 
glass,  Avhich  echoes  the  same  sound :  and 

2nd. — The  window-frame  being  shaken^ 
contributes  to  the  noise. 

Window  frames  are  shaken,  1. — By  sound-waves  impinging  against 
them;  2. — By  a  vibratory  motion  communicated  to  them  by  the  walls  of 
the  house. 

1766. 

Q.  Wliy  are  copper  and  iron  sonorous  and 
not  lead  ? 

A.  Copper  and  iron  are  hard  and  elastic  ; 
but  as  lead  is  neither  hard  nor  yet  clastic^ 
it  is  not  sonorous. 


TRANS^IISSION  OF  SOUND.  487 


1767. 

Q.  Of  what  is  hell-metal  made  ? 

A.  Of  copper  and  tin  in  the  following 
proportions  : — In  every  five  pounds  of  bell* 
metal  there  should  be  one  pound  of  tin,  au»1 
four  pounds  of  copper. 

1768. 

Q.  Why  is  this  mixture  of  tin  and  cop- 
per used  for  hell-metal  ? 

A.  Because  it  is  much  harder  and  more 
elastic  than  any  of  the  pure  metals. 

1769. 

Q.  Why  do  we  haar  a  hell  if  it  be  struck  ? 

A.  The  bell  vibrates,  and  in  its  agitation, 
compresses  the  air  to  a  certain  distance 
around  it,  at  each  vibration.  The  com- 
pressed air  instantly  expands,  and  in  doing 
so  repeats  the  pressure  on  the  air  next  in 
contact  with  it,  and  so  on;  as  a  pebble 
thrown  into  still  water  makes  waves  all 
around  it ;  diminishing  in  force,  the  more 
distant  they  are  from  the  original  stroke. 
The  air  thus  agitated,  reaches  the  ear  where 
a  similar  impulse  is  given  to  a  very  deli- 
cate membrane  and  the  mind  then  receives 
the  impression  of  sound, 

1770. 

Q.  How  can  a  bell  which  is  solid  be  said 
to  vibrate  ? 


488 


TRANSMISSION  OF  SOUND. 


A.  Although  the  metal  of  which  the  bell 
is  composed  is  solid,  yet  it  actually  changes 
its  form  every  time  it  is  struck,  and  its  par- 
ticles are  thereby  thrown  into  motion. 

1771. 

Q  Why  is  the  scAind  of  a  bell  stopped  by 
lunching  the  bell  with  our  finger? 

A.  Because  the  weight  of  our  finger  stops 
(he  vibrations  of  the  bell ;  and  as  soon  as 
the  bell  ceases  to  vibrate,  it  ceases  to  make 
sound-waves  in  the  air. 

1772. 

Q.  After  striking  a  finger  glass,  why  is 
the  sound  silenced,  upon  touching  the  glass 
with  your  finger  ? 

A.  Because  the  pressure  of  your  finger 
stops  the  vibrations  of  the  glass ;  and,  so 
soon  as  the  finger-glass  ceases  to  vibrate,  it 
ceases  to  make  sound-waves  in  the  air. 

1773. 

Q.  Why  does  a  split  bell  make  a  hoarse, 
disagreeable  sound  ? 

A.  Because  the  split  of  the  bell  causes  a 
double  vibration;  and  as  the  sound-waves 
dash  and  jar,  they  impede  each  other's  mo- 
tion^  and  produce  discordant  sounds. 

1774. 

Q,  Wliy  can  persons,  living  a  mile  or 


TRANSraSSION  OF  SOUND.  489 


two  from  a  town,  hear  the  hells  of  the  town 
churches  sometimes  and  not  at  others  ? 

A.  Because  fogs,  rain,  and  snow,  ol)- 
fetruct  the  passage  of  sound  ;  but  when  the 
air  is  cold  and  clear,  sound  is  propagated 
more  easily. 

1775. 

Q.  Why  can  we  not  hear  sounds  (as  those 
of  distant  church  bells)  in  rainy  weather  so 
well  as  in  fine  weather  ? 

A.  Because  the  falling  rain  interferes 
with  the  undulations  of  the  sound-waves,  and 
breaks  them  up. 

1776. 

Q.  Why  can  we  not  hear  sounds  (as  those 
of  distant  church  bells)  in  snowy  weather 
so  well  as  in  fine  weather  ? 

A.  Because  the  falling  snow  interferes 
with  the  undulations  of  the  sound-waves, 
and  stops  their  progress. 

1777. 

Q.  Why  can  we  hear  distant  clocks  most 
distinctly  in  clear,  cold  weather  ? 

A.  Because  the  air  is  of  more  uniform 
density,  and  there  are  fewer  currents  of  aii 
of  unequal  temperature  to  interrupt  tn€ 
Bound- waves. 

Besid  ;s,  dense  air  can  propagate  sound-waves  more  readily  than 


190 


TRANSMISSION  OF  SOVND. 


177a 

Q.  Why  can  persons  (near  the  poles)  hera 
the  voices  of  men  in  conversation  for  a  mile 
distant  in  winter- time  ? 

A.  Because  the  air  is  very  cold,  clear,  and 
si  ill ;  in  consequence  of  which,  there  are 
but  few  currents  of  air  of  unequal  tem- 
perature to  interrupt  the  sound-waves. 

Captain  Ross  heard  the  voices  of  his  men  in  conversation  a  mile  and  a 
half  from  ihe  spot  where  they  slood. 

1779. 

Q.  Why  are  not  sounds  (such  as  those  of 
distant  church  bells)  heard  so  distinctly  on 
a  hot  day  as  in  frosty  weather  ? 

A.  1st. — Because  the  density  of  the  air 
is  less  unifoim  in  very  hot  weather : 

2nd. — It  is  more  rarefied,  and,  conse- 
quently, a  worse  conductor  of  sound  :  and 

3rd. — It  is  more  liable  to  accidental  cur* 
rents,  which  impede  the  progress  of  sound, 

1730. 

Q.  How  do  you  know  that  rarefied  air  can^ 
not  transmit  sound  so  well  as  dense  air  ? 

A,  Because  the  sound  of  a  hell,  (in  the 
receiver  of  an  air-pump)  can  scarcely  he  heard^ 
after  the  air  has  been  partially  exhausted  ; 
and  the  report  of  a  pistol  (fired  on  a  high 
^^\ouIltain)  would  be  scarcely  audible. 


TRANSMISSION  OF  SOUND.  491 


1781. 

Q.  Wliy  does  the  sea  heave  and  sighy  just 
previous  to  a  storm  ? 

A.  Because  the  density  of  the  air  is  very 
mddenly  diminished  ;  and  (as  the  density  of 
the  air  is  diminished)  its  power  to  transmit 
sound  is  diminished  also ;  in  consequence 
of  which,  the  roar  of  the  sea  is  less  au- 
dible, and  seems  like  heavy  sighs. 

1782. 

Q.  Why  is  the  air  so  universally  quiet y 
just  previous  to  a  tempest  ? 

A.  Because  the  air  is  suddenly  and  very 
greatly  rarefied  ;  and  (as  the  density  of  the 
air  is  diminished)  its  power  to  transmit 
sound  is  diminished  also. 

1783. 

Q.  Why  can  we  not  hear  sounds  (such  as 
those  of  distant  clocks)  so  distinctly  in  a 
thick  mist  or  haze  as  in  a  clear  night  ? 

A.  Because  the  air  is  not  of  uniform 
density  when  it  is  laden  with  mist ;  in 
consequence  of  which,  the  sound-waves  are 
obstructed  in  their  progress. 

1784. 

Q.  Why  do  we  hear  sounds  better  by 
mght  than  by  day  ? 

A.  1st. — Because  night  air  is  of  more 


4.92  TEANSmSSION  OF  SOUND. 


uniform  density  and  less  liable  to  accidental 
currents:  and 

2nd. — Night  is  more  still  from  the  sus- 
pension of  business  and  hum  of  men. 

1785. 

Q.  Why  is  the  air  of  more  uniform  den* 
nty  hy  night  than  it  is  by  day  ? 

A.  Because  it  is  less  liable  to  accidental 
currents  ;  inasmuch  as  the  breezes  (created 
by  the  action  of  the  sun's  rays)  generally 
cease  during  the  night. 

1786. 

Q.  How  should  partition  walls  be  made^ 
to  prevent  the  voices  in  adjoining  rooms 
from  being  heard  ? 

A.  The  space  between  the  laths  should 
be  filled  with  shavings  or  saw-dust ;  and  then 
no  sound  would  ever  pass  from  one  room 
to  another. 

1787. 

Q.  Why  would  shavings  or  saw-dust^  pre- 
vent  the  transmission  of  sound  from  room 
to  room  ? 

A.  Because  there  would  be  sever ao  difcr-^ 
ent  media  for  the  sound  to  pass  through : 
1st — the  air;  2nd — the  laths  and  paper; 
Brd — the  saw-dust  or  shavings  ;  4th — lath 
and  paper  again  ;  5th — the  air  again  :  and 


TRANSMISSION  OP  SOUND 


493 


every  change  of  medium  diminislies  the 
strength  of  the  sound-waves. 

1788. 

Q.  Why  can  deaf  people  hear  through 
an  ear-trumpet? 

A  Because  the  ear-trumpet  restrains  the 
spreau  of  the  voice  and  limits  the  diameter 
of  the  sound-waves ;  in  consequence  of 
which,  their  strength  is  increased. 

1789. 

Q.  What  is  a  stethoscope  ? 

A.  It  is  an  instrument  which  resembles 
a  small  trumpet.  The  wide  mouth  is  ap- 
plied to  the  body  and  the  other  is  held 
to  the  ear  of  the  Physician,  who  can  hear 
distinctly  the  action  of  the  lungs  and  judge 
whether  they  be  healthy  or  the  reverse. 

1790. 

Q.  Why  does  sound  seem  louder  in  caves 
than  on  a  plain  ? 

A.  Because  the  sides  of  the  cave  con- 
line  the  sound-waves,  and  prevent  their 
spreading;  in  consequence  of  which,  their 
{frength  is  greatly  increased. 

1791. 

Q.  "Why  are  mountains  more  quiet  than 
plains  ? 

A.  Because  the  air  of  mountains  is  i^^ry 
42 


494  TRANSMISSION  OF  SOUND. 


rarefied ;  and,  as  the  air  becomes  rarefied^ 
Bound  becomes  less  intense . 

1792. 

Q.  How  do  you  know  that  the  rarity  of 

air  diminishes  the  intensity  of  sound? 

A.  If  a  bell  be  rung  in  the  receiver  of 
an  air-pump,  the  sound  becomes  fainter  and 
fainter  as  the  air  is  exhausted ;  till  at  last 
It  is  almost  inaudible. 

1793. 

Q.  A  person  situated  at  the  extremity  of 
a  wire  600  feet  in  length  will  hear  the  same 
sound  twice.    Explain  this  ? 

A.  The  air  is  not  so  good  a  conductor  of 
sound  as  the  iron  wire ;  therefore,  as  it 
passes  along  the  wire  almost  instantaneously^ 
it  requires  some  time  to  travel  the  same  dis- 
tance through  air. 

1794. 

Q.  Can  sound  be  heard  through  wafer  ? 

A.  Yes ;  a  bell  rung  under  water  can  be 
heard  above ;  and  if  the  head  of  the  audi- 
tor bo  under  water  at  the  time,  it  can 
be  still  more  distinctly  heard.  It  is  not 
however,  so  loud  and  clear  as  when  rung 
in  the  air. 

1795. 

Q.  If  from  an  eminence  you  look  dowD 


TRANSMISSION  OF  SOUND. 


495 


upon  a  long  column  of  soldiers  marching  to 
a  band  of  music  in  front,  those  in  the  rear 
will  step  a  little  later  than  those  some  dis- 
tance before  them.  Can  you  explain  the 
n)ason  of  this  ? 

A.  Each  rank  steps,  not  when  the  sound 
is  made,  but  when  in  its  progress  down  the 
column  at  the  rate  of  1142  feet  in  a 
second  of  time,  it  reaches  their  ears.  Those 
who  are  near  the  music  hear  it  first,  w^hile 
those  at  the  end  of  the  column  must  wait 
until  it  has  traveled  to  their  ears  at  the 
above  rate. 

1796. 

Q.  Why  does  a  rail- way  train  make  more 
noise  when  it  passes  over  a  bridge,  than  when 
it  runs  over  solid  ground 

A.  Because  the  bridge  is  elastic,  and  vi- 
brates much  more  from  the  weight  of  the 
train,  than  the  solid  earth ;  in  consequence 
of  which,  it  produces  more  definite  sound- 
waves. 

The  brid?:e  acts  as  a  sounding  board  ;  and  the  watc  '^r  earth  oelow  the 
bridge  repeats  the  sound. 

1797. 

Q.  Why  can  sounds  be  heard  (in  a  calm 
day)  at  a  s^r eater  distance  on  the  sea  than  on 
land^ 

A.  1st. —  -Because  the  air  over  the  sea  is 


496  TRANSMISSION  OP  SOUND. 


generally  denser  and   more   laden  with 
moisture,  than  the  air  over  the  land ; 
2nd. — The  density  is  more  uniform ;  and 
3rd. — VTater  being  more  elastic  than  land, 
is  a  better  propagator  of  sound. 

SECTION  I.  MUSICAL  SOUNDS. 

1798. 

Q.  What  are  musical  sounds  ? 

A.  Regular  and  uniform  successions  of 
vibrations. 

1799. 

Q.  What  is  the  difference  between  a  mu- 

9ical  sound,  and  a  mere  noise  ? 

A.  All  mere  noises  are  occasioned  by 
irregular  impulses  communicated  to  the  ear : 
but  in  order  to  produce  a  musical  sound,  the 
impulses,  and  consequently,  the  undulations 
of  the  air,  must  be  all  exactly  similar  in 
duration  and  intensity,  and  must  recur  after 
exactly  equal  intervals  of  time. 

1800. 

Q.  Do  all  persons  hear  sounds  alike  ? 
A.  No ;  that  faculty  seems  to  depend 
upon  the  sensihility  of  the  auditory  nerves. 

"  Auditory^"* — having  the  power  of  liearing. 
1801. 

Q.  What  are  the  boundaries  of  human  heat 
ing? 


MUSICAL  SOUNDS. 


497 


A  The  whole  range  of  human  hearing, 
from  the  lowest  note  of  the  organ,  to  the 
liighest  known  cry  of  insects,  as  of  the 
cri(5ket,  includes  about  nine  octaves, 

A-i  ears,  however,  nre  by  no  means  gifted  with  sf>  great  a  range  of  hear*, 
fcg  ;  man  J  persons,  vhough  not  at  ail  deaf,  are  quite  insensible  to  the  high 
^  t  )te2  of  some  insects. 

1802. 

Q  How  many  vibrations  of  a  nmsical 
chord  are  necessary  to  produce  a  definite 
sound  ? 

A.  When  the  vibrations  are  less  than  six- 
>een  in  a  second  of  time,  a  continued  sound 
cannot  be  communicated  to  the  ear. 

1803. 

Q.  How  manT/  vibrations  is  the  human  ear 
able  to  appreciate  ? 

A.  The  human  ear  is  capable  of  appreciat- 
ing as  many  as  twenty -four  thousand  vibra- 
Hons  in  a  second  of  time;  and,  is  consequently 
able  to  hear  a  sound  which  only  lasts  the 
twenty 'four  thousandth  part  of  a  second  ! 

1804. 

Q.  Why  are  some  notes  boss,  and  some 
treble? 

A.  Because  slow  vibrations  produce  oass 
or  deep  sounds;  but  quick  vibrations  produco 
shrill  or  treble  ones, 
42* 


198  TRANSMISSION  OF  SOUND 

1805. 

Q,  Why  do  musical  glasses  give  sounds  ? 

A.  Because  the  glasses  vibrate  as  soon  as 
they  are  struck,  and  set  in  motion  the  sound- 
waves of  the  air. 

1806. 

Q  Why  do  flutes y  etc.,  produce  musical 
rounds  ? 

A.  Because  the  breath  of  the  performer 
causes  the  air  in  the  flute  to  vibrate;  and  this 
vibration  sets  in  motion  the  sound-waves 
of  the  air. 

1807. 

Q.  Why  does  a  flddle-string  give  a  musi- 
cal sound  ? 

A.  Because  the  bow  drawn  across  the 
string  causes  it  to  vibrate;  and  this  vibration 
of  the  string  sets  in  motion  the  sound-vmves  of 
the  air,  and  produces  musical  notes. 

1808. 

Q.  Why  does  a  drum  sound  ? 

A.  Because  the  parchment  head  of  the 
drum  vibrates  from  the  blow  of  the  drum- 
stick, and  sets  in  motion  the  sound-waves 
of  the  air. 

1809. 

Q.  Why  do  piano-fortes  produce  musica] 

Hounds  ? 


ECHO. 


499 


A.  Because  each  key  of  the  piano  (being 
struck  with  the  finger)  Hfts  up  a  httle  ham- 
mer which  knocks  against  a  string;  and  the 
vibration  thus  produced  sets  in  motion  the 
sound-waves  of  the  air. 

1810. 

Q,  Why  is  an  instrument  flat  when  the 
strings  are  unstrung  ? 

A.  Because  the  vibrations  are  too  slow  ; 
m  consequence  of  which,  the  sounds  pio- 
duced  are  not  shrill  or  sharp  enough. 


SECTION  IT.  ECHO 

1811. 

Q.  What  is  echo? 

A.  Echo  is  reflected  sound. 

1812. 

Q.  What  is  the  cause  of  echo  ? 

A.  Whenever  a  sound-wave  striken 
against  any  obstacle  (such  as  a  wall  or  hill,) 
it  is  reflected  (or  thrown  back ;)  and  this  re- 
flected sound  is  called  an  echo. 

The  same  laws  govern  echo  as  light. 
1813. 

Q.  Wliat  places  are  most  famous  for  echo? 
A.  Caverns,  grottoes,  and  ruined  abbej^s; 
the  areas  of  halls;  the  windings  of  long  pas- 


500 


TRANSMISSION  OF  SOUND. 


sages ;  the  aisles  of  cathedral  churches  i 
moui)  tains  and  icebergs. 

1814. 

Q.  Why  are  caverns,  grottoes,  and  ruins, 
famous  for  echoes  ? 

A.  1st. — Because  the  sound-waves  can- 
not pass  beyond  the  cavern  or  grotto ;  and, 
therefore,  must  flow  hack;  and 

2nd. — The  return-waves  (being  entangled 
by  the  cavern)  are  detained  for  a  short  time, 
and  come  deliberately  to  the  ear. 

1815. 

Q.  Why  are  halls,  winding  passages,  and 
cathedral  aisles  famous  for  echoes  ? 

A.  Because  the  sound-waves  cannot  flow 
freely  forward;  but  perpetually  strike 
against  the  winding  walls,  and  are  beaten 
hack. 

1S16. 

Q.  Why  are  mountains  and  icebergs  fa- 
mous for  echoes  ? 

A.  Because  they  present  a  harrier  to  the 
sound-waves,  which  they  cannot  pass,  and  are 
sufficiently  elastic  to  throw  them  back. 

1817, 

Q.  ^Vliy  do  not  the  tmlls  of  a  room  or 
oluirch  j)roduce  echo. 

A.  Because  sound  travels  with  such  velch 


ECHO. 


501 


tity  that  the  echo  is  blended  with  the  original 
sound;  and  the  two  produce  but  one  impres- 
sion on  the  ear. 

Sound  travels  ihirteen  miles  in  a  minute  ;  and  no  echo  is  heard,  unless 
the  surface  (against  which  the  sound  strikes)  is  sixty-five  feel  from  ihe 
place  whence  the  sound  originally  proceeded. 

1818. 

Q.  Why  do  very  large  buildings  (as  cathe- 
drals) often  reverberate  the  voice  of  the 
speaker  ? 

A.  Because  the  walls  are  so  far  off  from 
the  speaker^  that  the  echo  does  not  get  back 
in  time  to  blend  with  the  original  sound ; 
and,  therefore,  each  is  heard  separately. 

1819. 

Q.  Why  do  some  echoes  repeat  only  one 
syllable  ? 

A.  Because  the  echoing  body  is  very  near. 
The  further  the  echoing  body  is  off,  the 
more  sound  it  will  reflect;  if,  therefore,  it  be 
very  near,  it  will  repeat  but  one  syllable. 

1820. 

Q.  Why  does  an  echo  sometimes  repeat 
two  or  more  syllables. 

A.  Because  the  echoing  body  is  far  off; 
and,  therefore,  there  is  time  for  one  reflec« 
tion  to  pass  away  before  another  reaches  the 
ear 


502 


MISCELLANEOUS. 


N.  B.  All  ihe  syllatles  must  be  uttered,  before  the  echo  of  fjt,  first  syL* 
ble  reaches  ihe  ear — if,  therefore,  a  person  repeats  seven  syllables  i;i  twc 
Beennds  of  time,  and  hears  thetn  all  echoed,  the  reflecting  object  is  1143 
feel  distant  ;  (because  sound  travels  1142  feet  in  a  second,  and  the  words 
lake  one  second  to  go  to  the  reflecting  object,  and  one  second  to  return.) 

1821. 

Q.  Why  are  two  or  more  echoes  sometimes 
heard  ? 

A.  Because  separate  reverberating  sur 
laces  receive  the  sound  and  reflect  it  in  suc- 
cession. 

Seventeen  miles  above  Glasgow,  (Scotland,)  near  a  mansion  called 
Rosneaih,  is  a  very  remarkable  echo.  If  a  trumpeter  plays  a  tune  and 
Btops,  the  echo  will  begin  the  same  tune  end  repeal  it  all  accurately  : — ai 
soon  as  this  echo  has  ceased,  another  will  echo  the  same  tune  in  a  lowei 
lone  ;  and  after  the  secorkd  echo  has  ceased,  a  third  will  succeed  with  equal 
fidelity,  though  m  a  much  feebler  tone. 

At  the  Lake  of  Kilkarney,  in  Ireland,  there  is  an  echo  which  plays  an 
excellent    second  "  to  any  simple  tune  played  on  a  bugle. 


MISCELLANEOUS. 

1822. 

Q.  Why  do  all  fruits,  etc.,  (when  severed 
from  the  tree,)  fall  to  the  earth? 
A.  Because  the  earth  attracts  them. 

1823. 

Q.  Why  do  the  hubbies  in  a  cup  erf  tei 
range  round  the  sides  of  the  cup  ? 
A.  Because  the  cup  attracts  them. 

1824. 

Q.  Why  do  all  the  little  bubbles  tend  to- 
wards the  large  ones  ? 

k..  Because  the  large  bubbles  (being  the 
superior  masses)  attract  them. 


MISCELLANEOUS. 


1825. 

Q.  Why  do  the  bubbles  of  a  cup  of  tea  foU 
low  a.  tea- spoon  ? 

A.  Because  the  tea-spoon  attracts  them. 

1S26. 

Q.  Why  are  the  dides  of  a  pond  covered 
with  leaves,  while  the  middle  of  the  pond  is 
quite  clear  ? 

A.  Because  the  shore  attracts  the  leaves 
to  itself. 

1827. 

Q.  Why  can  you  fill  a  dry  glass  beyond 
the  level  of  the  brim  ? 

A.  Because  the  mass  of  water  in  the  glass 
holds  the  overplus  back  by  the  attraction  of 
its  particles. 

1828. 

Q.  Why  is  a  lump  of  sugar  (left  at  the  bot- 
tom of  a  cup)  so  long  in  melting  ? 

A.  Because  (as  it  melts)  it  makes  the  tea 
above  it  heavier  ;  and  (so  long  as  it  remains 
at  tlie  bottom)  is  surrounded  by  tea  fully 
mtxtroted  with  sugar ;  in  consequence  of 
wliich,  the  same  portions  of  liquid  will  hold 
no  more  sugar  in  solution. 

1829. 

Q.  What  is  capillary  attraction  ? 

A.  Tlie  power  which  very  minute  tubes 


504 


mSCELLANEOUS. 


possess,  of  causing  a  liquid  to  rise  in  them 
above  its  level. 

Capillary^'''*  from  the  Latin  word  "  capillaris,*'  {like  a  hair;)  the  tubes 
referred  to  are  almost  as  fine  and  delicaie  as  a  hair.   Water  ascenda 
through  a  lump  of  sugar,  or  piece  of  sponge,  by  capillary  attraction. 
N«  B.  The  smaller  the  tube,  the  higher  will  the  liquid  be  attracted  by  )X. 

1830. 

Q  Why  does  water  melt  salt  ? 

A.  Because  very  minute  particles  of  wa- 
ter insinuate  themselves  into  the  pores  of 
the  salt,  by  capillary  attraction;  and  force 
the  crystals  apart  from  each  other. 

1831. 

Q.  Why  does  water  melt  sugar  ? 

A.  Because  very  minute  particles  of  wa- 
iter insinuate  themselves  into  the  pores  of 
the  sugar,  by  capillary  attraction;  and  force 
the  crystals  apart  from  each  other. 

1832. 

Q.  Why  is  vegetation  on  the  margin  of  a 
river,  more  luxuriant  than  in  an  open  field  ? 

A.  Because  the  porous  earth  on  the  bank 
draws  up  water  to  the  roots  of  the  plants  by 
capillary  attraction. 

1833. 

Q.  Why  do  persons  (who  water  plants) 
very  often  pour  the  water  into  the  saucer y 
and  not  over  the  plants  ? 

A.  Because  the  water  in  the  saucer  is 


MISCELLA]S.ROTTS. 


505 


drawn  up  by  the  mould  (throiigli  the  hole 
at  the  bottom  of  the  flower-pot)  and  is  trans- 
ferred to  the  stem  and  leaves  of  the  plant 
by  capillary  attraction. 

1834. 

Q.  If  you  leave  a  little  tea  in  your  cup, 
and  rest  your  spoon  on  the  bottom  of  the 
cup,  why  does  the  tea  rush  to  the  spoon? 

A.  Because  the  spoon  attracts  it,  by  what 
is  called  capillary  attraction. 

1835. 

Q.  If  a  drop  of  loater  be  spilled  on  a 
table-cloth,  why  will  it  spread  in  all  direc- 
tions ? 

A.  Because  the  threads  of  the  cloth  ab- 
sorb the  water  by  capillary  attraction. 

1836. 

Q,  Why  are  old  people  unable  to  walk  ? 
A.  Because  their  muscles  become  rigid. 

1837. 

Q.  Why  is  it  more  easy  to  simm  in  the 

sea  than  in  a  river  ? 

A.  Because  the  specific  gravity  of  salt  wa- 
ter is  greater  than  that  of  fresh ;  and,  there- 
fore, it  buoys  up  the  swimmer  better  ? 

1838. 

Q.  How  do  cooks  ascertain  if  their  br\m 
bo  salt  enough  for  pickling? 
43 


506 


MISCELLANEOUS. 


A  Tliey  put  an  egg  info  their  hrine.  II 
the  egg  sinks,  the  brine  is  not  strong  enough ; 
if  the  egg  floats,  it  is. 

1839. 

Q.  Why  will  an  egg  sink,  if  the  brine  be 
not  strong  enough  for  pickling  1 

A.  Because  an  egg  will  be  the  heavier ; 
but  if  as  much  salt  be  added  as  the  water 
can  dissolve,  an  egg  will  be  lighter  than 
the  strong  brine,  and  consequently  jSoat  on 
the  surface. 

1840. 

Q.  Why  will  an  egg  float  in  strong  brine, 
and  not  in  water  ? 

A.  Because  the  specific  gravity  of  salt 
and  water  is  greater  than  that  of  water  only. 

1841. 

Q.  Why  do  persons  sink  in  water  when 
they  are  unskillful  swimmers  ? 

A.  Because  they  struggle  to  keep  their 
head  out  of  water. 

1842. 

Q  Why  can  quadrupeds  swim  more  easily 
than  man  ? 

A.  1st. — Because  the  tru?ik  of  quadru- 
peds is  lighter  than  water  ;  and  this  is  tho 
greatest  part  of  them  ;  and 


MISCELLANEOUS. 


507 


2nd.— The  position  of  a  beast  (\^•bell 
8\^imming)  is  a  natural  one. 

1843. 

Q.  Why  is  it  more  difficult  for  a  man  to 
swim  than  for  a  heast  ? 

A,  1st. — Because  his  body  is  more  heavy 
III  proportion  than  that  of  a  beast;  and 

2nd. — The  position  and  muscular  action 
of  a  man  (when  swimming)  differ  greatly 
from  his  ordinary  habits ;  but  beasts  swim 
in  their  ordinary  position. 

1844. 

Q.  Explain  how  this  is  ? 

A.  When  the  head  is  thrown  back  boldly 
into  the  water,  the  mouth  is  kept  above  the 
surface,  and  the  swimmer  is  able  to  breathe. 

But  when  the  head  is  kept  above  the  sur^ 
face  of  the  water,  the  chin  and  mouth  sink 
beneath  it,  and  the  swimmer  is  suffocated. 

This  may  be  illustrated  thus: — If  apiece  of  wood  be  of  such  specific 
gravity,  that  o\\\y  two  square  inches  can  float  out  of  water  ;  it  is  manifest 
tljat  if  two  other  inches  are  raised  out,  the  two  former  inches  must  b*; 
plunged  in.  The  body  (in  floating)  resembles  this  piece  of  wood. — If  twci 
equ^re  inches  of  the  fa-^,  float  out  <if  the  water,  the  swimmer  can  breatl  e\ 
but  if  part  of  the  back  ar.d  crown  of  the  head  be  forcibly  raised  above  he 
surface,  a  proportional  quantity  of  the  face  must  be  plunged  in;  and  ina 
mouih  becomes  covered. 

1845. 

Q.  Why  can  fat  men  sivim  more  easily 
tlian  spa'^e  men  ? 

A.  Because  fat  is  lighter  than  water ;  and 


508 


MISCELLANEOUS. 


the  fatter  a  man  is,  the  more  buoyant  will 
he  be. 

1846. 

Q.  How  are  fishes  able -to  ascend  to  the 
sur  face  of  water  ? 

A.  Pishes  have  an  air-bladder  near  the 
abdomen ;  when  this  bladder  is  filled  with 
air,  the  fish  increases  in  size,  and  (being 
lighter)  ascends  through  the  water  to  its 
surface. 

1847. 

Q.  How  are  fishes  able  to  dive  in  a  min- 
ute to  the  bottom  of  a  stream  ? 

A.  They  expel  the  air  from  their  air-blad- 
der; in  consequence  of  which,  their  size  is 
diminished^  and  they  sink  instantly 

1848. 

Q.  Why  are  pearl  divers  very  frequently 
deaf? 

A.  Because  the  pressure  of  the  water 
against  the  tympanum  of  their  ears  ruptures 
the  membrane ;  and  this  rupture  produces 
incurable  deafness. 

1849. 

Q.  Why  do  divers,  when  they  are  under 
water,  suffar  great  pain  in  their  eyes  and 
ears  ? 

A.  Because  the  air  at  the  bottom  of  tht) 


IMISCELLANEOUS. 


509 


sea  IS  more  dense  than  the  air  on  the  surface  ; 
and  (till  the  air  inside  the  diver's  body  is 
settled  into  the  same  density)  he  feels  oj)- 
j)ressed  with  pain,  especially  in  the  earSc 

1850. 

Q.  Why  is  this  pain  felt  especially  about 
the  ears  of  a  diver? 

A.  Because  the  ear  is  fitted  with  a  small 
membrane  called  the  drum  (or  tympanum,) 
through  which  the  dense  air  bursts — the 
rupture  of  this  membrane  very  often  pro- 
duces incurable  deafness. 

When  tlie  diver  is  not  in  a  hell^  the  dense  water  bursts  into  his  ears  and 
ruptures  the  tympanum. 

1851. 

Q.  Why  will  not  beer  run  out  of  the  tub 
till  the  vent  peg  is  taken  out  ? 

A.  Because  the  upward  pressure  of  the 
external  air  (admitted  through  the  tap) 
holds  the  liquor  back — not  being  counter- 
balanced by  any  pressure  of  air  on  the  sur- 
face  of  the  liquid. 

The  uprvard  pressure  of  air  is  illustrated  by  the  followinof  simple  expert* 
Blent : — Fill  a  wine  glass  with  water;  cover  the  top  of  the  glass  with  a 
piece  of  writing  paper,  turn  the  glass  upside  down,  and  the  water  will  no: 
run  out.  The  paper  is  used  merely  to  give  the  air  a  medium  sufficiently 
dense  to  act  against. 

1852. 

Q.  Why  do  our  cm^ns  ache  just  previous 
fco  rain  ? 

A.  Because  our  feet  siveJHromthe  sudden 

43* 


510 


MISCELLANEOUS. 


depression  m  the  density  of  air,  and  iht 
bard  corn  (not  being  elastic)  is  painfully 
stretched  and  pressed. 

Some  of  this  pain  is  due  to  electricity. 
1853. 

Q.  When  liquor  is  decanted  or  poured  from 

bottle,  why  does  it  gurgle  ? 

A.  This  bubbling  noise  is  made  by  the 
air  rushing  into  the  bottle,  and  the  liquor 
bursting  out. 

The  liquor,  filling  the  neck  of  the  ooLtle,  prevents  the  air  from  getting 
freely  in ;  and  the  air  pressing  against  the  mouth  of  the  bottle,  prevents 
the  liquor  from  getting  freely  out ;  in  consequence  of  which,  the  air  bursis 
into  the  neck  of  the  bottle,  and  the  liquor  runs  from  the  same,  by  fits  ar.d 
starts,  as  either  is  able  to  prevail ;  as  this  process  is  repeated,  the  noise 
produced  is  called  a  gurgle. 

1854. 

Q.  Why  does  a  pop-gun  make  a  loud  re- 
port when  the  paper  bullet  is  discharged 
from  it  ? 

A.  Because  the  air,  confined  between  the 
paper  bullet  and  the  discharging  rod  is  sud- 
denly liberated,  and  strikes  against  the  sur- 
rounding air ;  this  makes  a  report  in  the 
same  way  as  when  any  two  solids  (such  as 
your  hand  and  the  table)  come  into  collision. 

1855. 

Q.  Why  are  some  parts  of  the  ceiling 
blacker  and  more  filthy  tlian  others  ? 

A.  Because  the  air  being  unable  to  pene- 
trate the  thick  joists  of  the  ceiling, /)n'59r.9  by 


MISCELLANEOUS. 


511 


(hose  parts,  and  deposits  its  soot  and  dust  on 
others  more  penetrable. 

N.  B.  The  site  of  this  deposit  of  soot  and  dust  is  frequently  deteimincd 
Ci  draughts  and  currents  of  air. 

1856. 

Q.  Why  are  the  ceilings,  which  are  never 
cleaned,  so  black  and  filthy  ? 

A.  Because  the  heated  air  of  the  room 
buoys  up  the  dust  and  fine  soot,  which  (be- 
ing unable  to  escape  through  the  plaster)  is 
deposited  on  the  ceiling. 

1S57. 

Q.  If  you  insert  a  straw  into  a  barrel  of 
cider,  wine,  etc.,  you  may  suck  the  liquid  at 
pleasure — explain  the  reason  of  this  ? 

A.  By  sucking,  all  the  air  is  exhausted  or 
drawn  out  of  the  straw ;  the  weight  of  the 
surrounding  air  causes  the  liquid  to  rush  in 
to  fill  the  vacuum  in  the  straw,  and  of 
course  flows  into  the  mouth 

1S58. 

Q.  If  a  flat  piece  of  moist  leather  be  put 
in  close  contact  with  a  stone  or  other  heavy 
body,  and  a  cord  be  attached  to  the  centre 
of  the  "leather,  the  stone  mav  be  lifted  by 
the  cord — explain  this  ? 

A.  The  air  is  excluded  between  the  lea- 
ther and  the  stone;  consequently,  a  vacuum 
is  formed,  and  owing  to  the  pressure  of  the 


512 


MISCELLANEOUS. 


atmosphere,  which  is  equal  to  fifteen  pounds 
for  every  square  inch,  the  leather  and  stone 
are  so  firmly  attached  together,  that  the 
weight  of  the  stone  is  not  sufficient  to 
separate  them. 

1859. 

Q  How  do  flies  and  other  insects  walk 
Dn  the  ceiling  ? 

A .  This  depends  on  the  formation  of  their 
feet,  which  act  in  the  manner  described  re- 
specting the  leather  and  the  stone.  Their 
feet  act  as  suckers,  excluding  the  air  be- 
tween them  and  the  ceiling  or  surface,  with 
which  they  are  in  contact,  and  the  atmo- 
•spheric  pressure  keeps  the  insect  from  fall- 
ing. 

I860. 

Q.  Why  do  the  sails  of  a  wind-mill  turn 
round  ? 

A.  Because  the  wind,  blowing  against 
the  oblique  surface  of  the  sails,  pushes  them 
out  of  the  way,  driving  them  from  place  to 
place  in  a  restless  round. 

1861. 

Q.  Why  does  a  piece  of  sugar  (held  in  a 
spoon  at  the  top  of  our  tea)  melt  very  ra- 
pidly ? 

A.  Because,  as  the  tea  becomes  sweet- 
med,  it  descends  to  the  bottom  of  the  cup  by 


MISCELLANEOUS. 


513 


its  own  gravity ;  and  fresh  portions  of 
unsweetened  tea  are  brought  constantly  iiito 
contact  with  the  sugar,  till  the  lump  is  en* 
tirely  dissolved. 

1862. 

Q.  Why  does  the  lump  of  sxigar  melt  mov^ 
quickly  when  stirred  about  ? 

A.  Because  fresh  portions  of  unsaturated 
tea  come  in  contact  with  the  lump,  and  soon 
dissolve  it. 

1863. 

Q.  Why  does  water  freeze  more  quickly 
than  milk  ? 

A.  Because  milk  contains  certain  salts  in 
solution ;  in  consequence  of  which,  it  re- 
quires a  greater  degree  of  cold  to  congeal  it 
than  water. 

Water  freezes  at  32°,  but  saZi  and  water  will  not  freeze  unless  the 
ihermometer  sinks  below  T^. 

1864. 

Q.  When  the  plants  called  trefoil,  dande- 
lion,  pimpernel,  etc.,  fold  up  their  leaves,  rain 
is  always  close  at  hand — explain  this  ? 

A.  1st. — The  cloudy  weather  diminishes 
the  light  of  the  sun  ;  and  without  the  stimu- 
lus of  sun-light,  these  flowers  never  open 
their  leaves 

2nd. — The  vapor  of  the  damp  air,  in- 
ginuating  itself  into  the  air- vessels  of  these 


514 


MISCELLANEOUS. 


delicate  plants,  causes  them  to  expand ;  in 
consequence  of  which,  the  leaflets  contiad 
and  close. 

All  these  plants  close  at  sun-set  also 
1865. 

Q  Why  is  not  the  air  which  passes  over 
water  so  cool  as  that  which  passes  over  land? 

A.  Because  loater  does  not  cool  down  at 
sun-set  so  fast  as  land  does ;  and,  therefore, 
the  air  in  contact  with  it  remains  warmer. 

1866. 

Q.  Why  does  not  water  cool  down  so  fast 

as  land  ? 

A.  1st. — Because  the  surface  of  water  is 
perpetually  changing;  and,  as  fast  as  one 
surface  is  made  cold,  another  is  presented ; 
and 

2nd. — The  moment  water  is  made  cold 
it  sinks,  and  warmer  portions  of  watei  rise 
to  occupy  its  place ;  therefore,  before  the 
surface  of  the  water  is  cooled,  the  whole  volumt 
must  be  made  cold ;  which  is  not  the  3ase 
with  land. 

1867. 

Q.  What  is  the  difference  between  a  goi 
Rnd  a  liquid  1 

A.  Gases  are  elastic,  but  liquids  not. 


MISCELLANEOUS. 


515 


1868. 

Q.  Illustrate  what  is  meant  by  ''the  elas- 
ticity of  gas 

A.  If  from  a  vessel  full  of  gas,  Tidf  were 
taken  out,  the  othn  half  would  immediately 
spread  itself  out,  and  fill  the  same  space  as 
was  occupied  by  the  whole. 

1869. 

Q.  Prove  that  a  liquid  is  not  elastic  ? 

A.  If  from  a  gallon  of  water  you  take 
half^  the  remaining  four  pints  will  take  up 
only  half  the  room  that  the  whole  gallon 
previously  did ,  a  liquid^  therefore,  is  not 
elastic  like  gas. 

Strictly  P|^eaking,  a  liquid  is  slightly  elastic  ;  inasmuch  as  it  may  be  com- 
'presied',    ud  will  afterwards  recover  its  former  dimensions. 

1870. 

Q.  How  can  a  sick  room  be  kept  free  from 
unhealthy  effluvia? 

A.  By  sprinkling  it  with  vinegar  boiled 
with  myrrh,  or  camphor ;  or  with  chloride 
of  lime. 

1871. 

Q  When  infectious  diseases  prevail,  how 
can  the  contagious  matter  be  removed  from 
bed-rooms,  hospitals,  houses,  etc.  ? 

A.  By  using  a  solution  of  chlorine,  of 
sulphurous  acid ;  which  will  not  onb*  rc- 


516 


MISCELIANEOire 


move  the  contagious  matter,  but  also  the 
offensive  smell  of  a  sick  room. 

1872. 

Q.  Why  does  chloride  of  lime  fumigate  a 
sii'k  room 

A.  Because  the  chlorine  absorbs  the  hj^ 
drogen  of  the  stale  air;  and  by  this  means 
removes  both  the  offensive  smell  and  the  in- 
fection of  a  sick  room. 

1873. 

Q.  Why  should  bed-rooms,  cottages,  hos- 
pitals,  and  stables,  be  occasionally  white- 
washed ? 

A.  Because  the  lime  is  very  caustic,  and 
removes  all  organic  matters  adhering  to  the 
w^alls. 

1874. 

Q.  Why  does  lime  destroy  the  offensive 
smells  of  bins,  sewers,  etc.  ? 

A.  Because  it  decomposes  the  offensive 
gases  upon  which  the  smell  depends,  and 
destroys  them. 

1875. 

Q.  What  is  sponge  ? 

A.  It  is  a  cellular  fibrous  substance,  pro- 
duced by  minute  animals  which  live  in  the 
sea ;  these  animals  are  called  polypi  by  na* 
turalists. 


MISCELLANEOUS. 


517 


Sponges  occur  attached  to  stones  at  the  bottom  of  the  sea,  and  abound 
Ipoii  the  shores  of  the  Islands  of  the  Grecian  Archipelago. 
They  afford,  on  distillation,  a  considerable  quantity  of  ammonia. 

1876. 

Q   Why  does  a  wet  sponge  dean  a  slate  ? 

A.  Because  the  water  holds  in  solution 
the  pencil  marks  made  on  the  slate ;  and 
the  mechanical  friction  employed  in  wiping 
the  slate,  detach  the  particles  of  pencil 
dust. 

1877. 

Q.  Why  does  Indian-rubber  erase  pencil 
marks  from  paper  ? 

A.  Because  Indian-rubber  contains  a  very 
large  quantity  of  carbon  ;  black-lead  is  car- 
bon and  iron. 

Now,  the  carbon  of  the  Indian-rubber 
has  so  great  an  attraction  for  the  black-lead, 
that  it  takes  up  the  loose  traces  of  it  left 
on  paper  by  the  pencil. 

Caoutchouc  or  Indian-rubber  is  a  compound  of  carbon  and  hydrogen, 
in  the  proportion  of  90  parts  of  carbon  to  10  parts  of  hydrogen. 

Graphite,  plumbago  or  black-lead  is  a  mineral  substance,  composed 
chiefly  of  carbon  with  a  very  small  proportion  of  iron.  That  used  for 
making  pencils  is  chiefly  procured  from  the  mines  of  Borrowdale  in  Cum- 
oerland. 

1878. 

Q.  How  is  the  green  fire  of  fire-works  pro- 
duced ? 

A.  By  the  nitrate  of  barytes  which  bums 
with  a  green  hue. 

*•  Barytes  "  so  called  from  a  Greek  word  (B<i/)uS'— Barus,)  whic^  Rfiu 
fies  heavy. 

44 


518 


MISCELLANEOUS. 


1879. 

Q.  How  IS  the  red  fire  of  fire- works  pro 
(laced  ? 

A.  By  the  nitrate  of  strontian,  which 
bums  with  a  red  hue. 

1880. 

Q.  How  is  the  white  fire  of  fire-works 
produced  ? 

A.  By  igniting  a  mixture  of  sulphur, 
nitre  and  charcoal — or  nitre,  sulf)hur  and 
Bulpliuret  of  antimony. 

1881. 

Q.  How  is  the  blue  fire  j)roduced  ? 
A.  By  igniting  gunpowder,  nitre,  sulphur 
and  zinc. 

1882. 

Q.  Wliy  do  plants  often  grow  out  of  walls 
and  towers  ? 

A.  Because  the  seed  has  been  blown 
there  with  the  dust,  by  the  wind,  or 
dropped  by  some  bird  flying  over. 

1883. 

Q.  Explain  how  manure  makes  land  fefr 
tile? 

A.  As  plants  extract  a  certain  amount 
of  salts  from  the  soil,  which  are  entirely  re- 
moved at  harvest,  it  is  obvious  that  the  soil 
will  become  gradually  impoverished,  unless 


MISCELLANEOUS. 


519 


these  matters  are  restored ;  this  restoro/- 
tion  is  accomplished  by  manuring  the  soil. 

1884. 

Q.  Why  is  guano  valuable  as  a  manure  ? 
A.  Because  it  contains  nitrogen  and  am- 
monia,  both  of  which  are  essential  to  plants. 

Those  species  of  guano  which  contain  the  largest  proportion  of  ferliliz- 
jDg  matter  (nitrogen  and  phosphates)  are  the  most  valuable. 

Guano  is  found  upon  the  coasts  of  Peru,  in  the  islands  of  Chinche,  near 
Pisco,  and  several  other  places  more  to  the  south.  It  forms  a  deposit  50 
or  60  feet  thick,  and  of  considerable  extent ;  and  appears  to  be  the  accu- 
mulation of  the  excrements  of  innumerable  flocks  of  birds,  especially 
herons  and  flamands,  which  inhabit  these  islands.  It  is  an  excellent  ma- 
nure, and  forms  the  object  of  a  most  extensive  and  profitable  trade. 

1885. 

Q.  What  is  the  use  of  lime,  marl,  etc., 
as  manure  ? 

A.  1st. — They  decompose  vegetable  sub- 
stances; and 

2nd. — They  liberate  the  alkalies  in  union 
with  the  silica  of  the  soil. 

1886. 

Q.  The  soil  contains  carbonic  acid,  from 
whence  is  this  derived  ? 

A.  1st. — From  the  air ;  from  which  it  ia 
driven  by  falling  showers ; 

2nd. — From  the  decomposition  of  vege- 
table and  animal  matters,  which  always 
produces  this  gas  in  abundance  ;  and 

3rd. — All   lime-stone,  chalk,  and  cal- 


520 


MISCELLANEOUS. 


careous  stones,  contain  vast  quantities  of 
carbonic  acid  in  a  solid  state. 

Calcareous,  that  is,  of  a  limy  nature. 
1887. 

Q.  Why  are  green  gooseberries,  currants^ 
etc.,  hard  ;  and  ripe  ones  soft? 

A.  Because  they  contain  an  infinite  num* 
ber  of  little  cells,  with  thick  walls ;  these 
become  thinner  from  day  to  day,  as  the 
fruit  ripens,  until  they  break;  when  the 
fruit  becomes  soft. 

1888. 

Q.  IVhy  does  currant  juice  when  boiled 
with  sugar  form  a  jelly  ? 

A.  Because  the  currant  juice  contains 
pectine  ;  a  gelatinous  matter  which  abounds 
in  many  fruits.  The  consistence  of  cur- 
rant and  other  fruit  jellies  is  ascribed  to 
this  substance. 

1889. 

Q.  Why  do  the  Laplanders  wear  skim 
with  the  fur  inwards  ? 

A.  Because  the  dr^j  skin  prevents  the 
loind  from  penetrating  to  their  body ;  and 
the  air  (between  the  hairs  of  the  fur)  soon 
becomes  heated  by  the  body  ;  in  consequence 
of  which,  the  Laplander  in  his  fur  is  clad 
in  a  case  of  hot  air^  impervious  to  the  a^Zd 
and  wind. 


MISCELLANEOUS. 


521 


1890. 

Q,  A  late  spring  makes  a  fruitful  year. 
Explain  the  reason  of  this. 

A.  If  the  vegetation  of  spring  be  hack^ 
ward,  th(3  frosty  nights  will  do  no  harm  ; 
for  Ihe  fruits  and  flowers  will  not  put  forth 
(heir  tender  shoots,  till  the  nights  become 
too  warm  to  injure  them. 

1891. 

0  Why  does  iron  turn  first  redy  then 
white  from  heat? 

A.  Light  and  heat  depend  u]3on  vibra- 
tions ;  the  more  rapid  the  vibrations,  the 
more  intense  the  light  and  heat;  white  heat 
is  a  more  intense  degree  of  heat  than  red 
and  occurs  only  when  the  vibrations  are 
most  rapid. 

Candescence  occurs  when  bodies  are  heated  to  800° — It  begins  with  a 
dull  red  color,  passes  to  an  orange  lint,  and  ultimately  to  a  shining  white. 

The  more  perfect  the  combustion  of  carbon  the  whiter  its  color. 

Probably  these  varying  colors  depend  upon  some  variety  in  the  thick- 
ness of  the  molecules  of  the  heated  substance,  caused  by  the  influence  of 
heat :  wliert-by  it  is  made  to  reflect  difTerenl  colors  according  to  the  vary 
ing  thickness  of  the  molecules.  But  this  subject  is  not  weii  understocxi  a! 
present, 

1892. 

Q.  What  causes  the  disease  commonly 
called  the  itch  ? 

A.  It  is  produced  by  an  insect  called  the 
'^itch  insect/'  which  burrows  in  the  slvin, 
ttud  is  greatly  encouraged  by  filth.  Suh 
44* 


522 


MISCELLANEOUS. 


phur,  corrosive  sublimate,  etc.,  will  destrojp 
the  insect,  and  cure  the  disease. 

Corrosive  sublimate  is  made  of  200  parts  of  mercury  with  72  of  chlo- 
rine. 

1893. 

Q.  When  wine  is  spilled  on  a  table-doth 
or  napkin,  how  can  the  stai7i  be  removed  ? 

A.  By  dipping  it  in  a  weak  solution  of 
chlorine. 

Chlorine  is  a  principle  ingredient  in  bleaching-powder. 
1894. 

Q.  When  wine  is  spilled  on  a  table-cloth 
etc.,  why  do  persons  generally  cover  the 
part  immediately  with  salt  ? 

A.  Because  salt  is  a  compound  of  chlo- 
rine  and  sodium ;  and  the  chlorine  of  the 
salt  acts  as  a  bleaching  powder. 

1895. 

Q.  Why  are  books  discolored  by  age  or 

damp  ? 

A.  Because  the  fibre  of  the  paper  be- 
comes partially  decomposed,  and  various 
impurities,  from  the  atmosphere  (or  othei 
.sources)  become  mixed  with  it. 

1896. 

Q.  Why  does  waxing  cotton  or  thread 
make  it  stronger  ? 

A  Because  it  cements  the  loose  fila^ 


MISCELLANEOUS. 


523 


ments  to  the  cord ;  and  makes  the  strands 
of  the  thread  more  compact. 

The  "  filaments  "  are  the  loose  fibres  of  the  cotton. 

The     strands  "  are  the  twists  or  single  yarns  twisted  into  a  tiiread. 

1897. 

Q.  Some  sweet  cakes  are  crisp  and  hard 
when  baked,  but  if  sal-oeratus  be  mixed 
with  the  dough,  they  will  be  soft.  Why 
is  this  ? 

A.  Sal-oeratus  has  an  affinity  for  moist- 
ure, which  it  absorbs  from  the  atmosphere, 
and  this  moisture  tends  to  keep  the  cakes 
soft. 

1898. 

Q.  How  does  starch  assist  in  giving  a 
smooth  glazed  surface  to  linen  ? 

A.  It  fills  up  the  interstices  between  the 
threads ;  and  makes  the  fabric  of  more 
uniform  density. 

"  Interstices  between  the  threads," — that  is,  the  small  groove  or  space 
between  each  thread. 

1899. 

Q.  How  does  starch  stiffen  linen  ? 

A.  By  filling  the  interstices  of  the  linen, 
by  which  means  it  is  rendered  more  rigid 
and  firm. 

1900. 

Q.  The  hooked  top  of  walking-sticks  is 
made  by  hailing  the  end  of  the  stick,  and 


524 


MISCELLzlNEOUS. 


then  bending  it  into  an  arcli.  Wliy  h  a 
stick  made  flexible  by  boiling  ? 

A,  Wood  contains  many  substances  sola- 
hie  in  hot  water,  as  starch,  sugar,  gum,  etc., 
and  several  others,  which  are  softened  by 
it ;  as,  therefore,  several  substances  are 
dissjlvedy  and  others  softened  by  boiling  wa- 
ter, the  stick  is  rendered  flexible. 

Celkular  fibre  and  woody  matter,  when  boiled  in  water,  become  scft 
and  geialinous. 

1901. 

Q.  Why  does  the  sun  or  fire  warp  wood  ? 

A.  Because  heat  draws  out  the  moisture 
from  that  part  of  the  wood  which  faces  it, 
and  causes  the  heated  surface  to  shrink  ;  as. 
therefore,  the  heated  surface  of  the  wood 
shrinks,  and  is  smaller  than  the  other  sur- 
face, it  draws  it  into  a  curve,  and  the  wood 
is  w^arped. 

1902. 

Q.  If  you  scrape  a  slip  of  paper  with  a 
knife,  why  will  the  paper  curl  ? 

A.  Because  the  under  surface  of  the  pa- 
per is  contracted  by  scraping,  which  brings 
the  particles  closer  together ;  this  contrac- 
tion of  the  under  surface  bends  the  slip  of 
paper  into  a  curl  or  arch. 


MISCELLANEOUS.  525 
1903. 

Q.  Why  do  plants  which  are  kopt  at  a 
window  hend  toward  the  glass? 

A.  Because  the  side  away  from  the  light 
grows  faster,  than  the  side/izcmg  the  hgbfc, 
and  pushes  the  top  of  the  plant  over  in  a 
curve. 

Woody  tissue  is  deposited  in  the  stem,  most  abundnntly  on  ne  sid^ 
nearest  the  light  ;  and  where  wood  is  formed  most,  growth  is  slowest,  be» 
cause  the  part  is  less  succulent. 

Wood  is  warped  by  the  fire,  because  the  under  surface  is  smaller  than 
the  upper ; 

And  paper  is  made  to  curl  by  scraping  the  under  surface  with  a  knife 
for  the  same  reason. 

1904 

Q.  When  a  candle  is  blown  out,  whence 
arises  the  offensive  odor? 

A.  The  tallow  distils  a  substance  in  the 
smoke,  called  acrr/le  ;  which  has  a  very  of- 
fensive smell. 

"Acryle,"  from  two  Greek  words  (aKpri-v\r]^  akre-ule)  the  basis,  or 
principle  of  a  wick  or  end,  that  is,  the  odor  which  issues  from  a  wick-end 
after  it  has  been  blown  out. 

1905. 

Q.  If  a  silver  spoon,  which  has  been  tar- 
nished by  an  egg,  be  rubbed  with  a  little 
salt — why  will  the  tarnish  disappear  ? 

A.  The  tarnish  in  this  case  is  sulphnrei 
of  silver,  produced  by  the  sulphur  of  the 
egg  combining  with  the  silver  spoon.  Salt 
acts  upon  this  sulphuret  of  silver ;  thus — 

The  sodium  of  the  salt  combines  with  the 
Bulphur,  and  produces  sulphate  of  sod^i. 


52t) 


MISCELLANEOUS. 


The  sulphur  being  thus  taken  away  froni 
the  silver,  the  tarnish  disappears. 

"  Sulphate  of  silver,"  that  is,  sulphur  in  combination  with  silver. 
Common  salt  is  a  compound  of  the  metal  called  sodium,  and  the  git 
tailed  chlorine. 

"  Sulphate  of  soda,"  is  a  combination  of  sulphuric  acid  and  soda. 
1906. 

Q.  Why  does  a  black  hat  turn  red  at  the 

sea-side  ? 

A.  Because  the  muriatic  acid  of  the  sea 
water  disturbs  the  gallic  acid  of  the  black 
dye,  and  turns  it  red. 

1907. 

Q.  What  is  an  excellent  remedy  against 
rats  and  mice  ? 

A.  Sulphuretted  hydrogen.  All  that  is 
necessary,  is  to  introduce  the  beak  of  a  re- 
tort into  a  rat-hole,  while  sulphuretted  hy- 
drogen is  being  given  off.  It  will  destroy 
the  rats,  and  make  the  hole  unj&t  for  others 
to  frequent. 

Sulphuretted  hydrogen  is  made  thus  :  Put  into  a  retort  or  glass  oottle,  a 
quantity  of  sulphuret  of  iron,  prepared  by  heating  arod  of  iron  red  hot;  bring 
:l  in  co)it!ic.t  with  a  roll  of  sulphur — this  will  form  sulphuret  of  iron,  which 
let  drop  into  water  ;  pour  over  it  a  small  portion  of  waler,  and  then  add 
Bu  equal  quantity  of  sulphuric  acid;  sulphuretted  hydrogen  will  be  given 
off  most  copiously. 

1908 

Q.  Why  are  hams  preserved  by  smoking 
them? 

A.  Because  the  smoke  of  a  wood  fire  con- 
tains creasote,  v^^hich  is  a  great  preservative 
of  all  animal  substances. 


MISCELLANEOUS. 


527 


1909. 

Q   What  is  common  marking  ink  ? 

A.  There  are  generally  two  bottles — one 
containing  a  solution  of  the  carbonate  of 
soda,  and  another  containing  a  solution  of 
nitrate  of  silver.  The  cloth  is  first  moistened 
with  the  carbonate  of  soda,  dried,  smooth- 
ed, and  then  written  on  with  a  pen  dipped 
in  the  nitrate  of  silver. — An  oxide  of  silver 
is  thus  precipitated,  and  leaves  a  black  mark 
behind. 

1910. 

Q.  Why  is  sorrel  sometimes  used  to  re- 
move ink  spots  from  linen  ? 

A.  Because  it  contains  oxalic  acid. 

Oxalic,  from  the  Greek  word  o^aXtr  (oxalis)  soml.  Oxalic  acid  is 
eometimes  erroneously  called  "  salt  of  lemons.''^ 

1911. 

Q.  Why  does  oxalic  acid  take  out  ink 
spots  ? 

A.  Because  it  dissolves  the  tannafe  of  iroUy 
of  which  the  black  portion  of  the  ink  con- 
gists 

Tan.iate  of  iron,"  is  tannic  acid  combined  with  iron.  Tannic  acid.  U 
Ihe  acid  of  tan;  or  oak  bark. 

1912. 

Q.  Why  do  laundresses  put  their  linen  in 
the  sun  to  whiten  ? 

A.  This  question  is  rather  difficult  to 
solve.    The  most  probable  solution,  is,  that 


528 


mSCELLANEOUS. 


air,  and  moisture  (arising  from  rain,  dew 

or  artificial  sprinkling)  influenced  by  solai 

light,  oxidize  the  color  on  the  fibre,  even 
without  the  assistance  of  alkali. 

1913. 

Q.  ^Yhy  do  bricks  turn  green  on  being  ex- 
posed for  some  time  to  the  weather,  espe- 
cially if  deprived  of  the  rays  of  the  sun  ? 

A.  The  "  green"  is  a  moss  or  lichen,  which 
grows  on  the  bricks,  and  thrives  better  in 
the  shade,  than  in  the  sun.  The  seeds  of 
this  moss  are  sujoposed  to  be  scattered  by 
the  winds. 

1914. 

Q.  The  ivhite  of  egg  is  generally  mixed 
with  ground  coffee  before  it  is  put  over  the 
fire  to  boil — ^why  is  this  done  ? 

A.  Because  the  albumen  contained  in  the 
white  of  the  egg  coagulates  while  boiling, 
and  entangles  the  small  particles  of  coffee, 
called  ''grounds,"  with  it;  which  fall  to  the 
bottom  of  the  pot,  and  leave  the  liquid  clear. 

1915. 

Q.  Why  does  wafer  rot  wood  ?  and,  why 
does  air  rot  wood  ? 

A.  Because  it  converts  the  solid  part  of 
the  wood  into  what  is  called  humus ^  by  oxi- 
dation ;  thus — 


raSCELLANEOUS. 


529 


1st. — The  cai'hon  of  the  wood  is  oxidized 
i»ito  carbonic  acid  ;  and 

2nd. — The  hydrogen  of  the  wood  is  oxi- 
dized into  water.  The  residue  becomes 
hunms  or  mould. 

The  Mack  mould  of  our  garoens,  is  called  humus^  and  is  produced  by  the 
i*"ay  of  vegetable  matter,  by  the  action  of  air  and  water. 

1916. 

Q.  Why  does  bread  become  mouldy  after 
it  has  been  kept  for  some  time  ? 

A.  Because  the  spores,  of  the  mould 
fungus,  floating  in  the  air,  fix  themselves 
in  the  decaying  bread  and  germinate. 

Fungi  germinate,  only  in  decaying  bodies. 

Spores,  or  Sporules,  from  the  Greek  word  ((rrropa — seed)  is  a  word  used 
by  botanist?^  to  indicate  the  seed  of  crypiogamic,  or  flowerless  plants; 
they  differ  from  seeds,  in  this  respect,  every  part  of  the  spore  shoots  into 
a  plant,  and  not  one  particular  poiiU  alone,  as  in  common  seeds. 

1917. 

Q.  Why  does  the  expansion  of  air  (at  the 
end  of  an  egg)  make  it  feel  warm  to  the 
tongue  ? 

A.  Because  air  is  a  very  bad  conductor;, 
and  the  more  air  an  egg  contains,  the  less 
heat  will  he  drawn  from  the  tongue  whon  it 
touches  the  shell. 

1918. 

'  Q.  Why  will  a  new-laid  egg  feel  colder  to 
the  tongue  at  the  thick  end  than  a  stale 
one  ? 

45 


530 


MTSOELL/VNEOUS. 


A.  Because  it  contains  more  whfe  and 
less  air ;  and  as  the  white  of  an  egg  is  a  bet- 
ter conductor  than  air,  the  heat  of  the 
tongue  will  be  drawn  off  more  rapidly.,  and 
the  egg  feei  coW^r. 


INDEX. 


A. 

Jlbsfrber  of  heat,  iron  bad,  150. 

not  reflector,  145. 

A'worpUon,  149. 

and  conduction,  difference 

between,  149. 
of  light,  429. 
Accidental  color,  482. 
Acetic  acid,  320. 
Acid  acetic,  320. 

citric,  319. 

lactic,  319. 

malic,  318. 

CBuanthic,  318. 

oxalic,  antidote  for,  326. 

pru>sic,  antidote  for,  324. 

tannic,  318. 

tarf.iric,  319. 
Aftryle,  525. 

Action,  cliemical,  a  source  of  heat, 
43. 

mechanical,  161. 

heat  produced  by,  161. 
Activity  agreeable  in  cold  weather, 
312. 

Adhesive,  glue,  129. 

gum,  129. 
paste,  129. 
starch,  129. 
Aeiated  water,  217. 
Air,  193. 

a  had  conductor,  85,  87,  89,  90, 

91,  104,  153. 
absorbs  heat,  151. 
a  non-conductor,  31. 
apple?  contain  more  than  chest- 
nuts, 46. 
alm:)Spheric,  193. 
between  the  fibres  of  wool,  89. 
blovv^  obliquely  into  the  fire,  75. 
chamber,  52. 

CO.  J,  condenses  vapor,  134. 
comes  down  the  chimney,  69. 
composed  of  nitrogen,  193. 

why,  194. 
condensed  bv  cold.  320. 
Eooled.  329  32^>. 


Air,  ctt.  rents  of  343,  514. 

in  a  room,  61. 
ovei  land,  400. 
danip,  iron  rusts  in,  177.  173. 
den'-ity  of,  dnninished,  390. 

previous  to  a  storm,  331 
draws  away  heal  from  us,  88. 
effeL-t  o(  cold  upon,  329. 
effect  of  heat  on,  332. 
expanded  by  heal,  43,  338. 
expulsion  of,  45. 

c;«uses  wind,  349 
filled  with  odor  before  rain,  133^ 

fire  burns  better  in  the,  241. 
supplied  with,  'iS. 

oy  a  tube,  69 

gun,  168. 

heal  '^xpands,  332. 

o/  affects  mercury,  333. 
swells,  in  a  bladder,  43. 
heatr-l,  103 

how,  323. 
a  conductor,  23. 
by  convection,  87. 
horses  snuff  up,  before  rain,  13t 
hot,  houses  heated  with,  51. 

c  a  sunny  day  104. 
hotter  ihan  our  bodies,  15-4. 
in  an  apple,  4(>. 
our  bodies,  369. 
an  e^rg,  529. 
lightning  purifies  the.  \f} 
linen  •tried  in  the,  125. 
mateiial,  191. 

moisture  of,  dissolves  salt,  \^ 
more  subtile  than  water,  86. 
motes,  if  dust  in,  1U6. 
never  at  rest,  87. 

mdintes  heat,  335. 
nitric  ocid  purifies  the,  38. 
not  heated  by  the  sun,  10-1, 

invisible,  194,  195. 
of  aro.jm  always  iu  motioUj  ffl 
151. 

ciri^^s  nnpure,  206,  SOS 
eoui.'ry  pure,  205. 

531 


532 


INDEX. 


Air  of  uiiif.irni  (U-iiKity  ni  iiiplii,  402. 
on  llii-  eurf.irr  ..('  liw  ciirili,  144. 
one      (.•fjld-  r  ili  iii  .iiioilicr, 
optn,  bed  f..i  Ih'  nil,  '^05. 
out  of  (Joora  ii.  ,-<•,  •ill. 
over  waiter,  .'51 !. 
purted  liy  liRlilnint;,  31. 
pro|K)riion3  of  IkjI,  destroyed, 
3(U. 

Tire,  wlieru  t)icr«  are  few  iu- 

habiJHnl?, 'JO.'), 
quiet  before  a  siorm,  491 . 
ruin  coo).«»  tlie,  125. 
rarefiiciion  of,  (>(J. 
rarefied,  ai>ceiiils,  GG. 

Ji(iuri8lie8  the  fire  lit- 
tle, 240. 
refracts  Iig:lit,  4(il . 
resisis  the  passjige  of  liphtning, 
31. 

rusts  iron,  170. 
seeks  an  f(|uilil)rium,  338. 
trees  rcncUr  it  wliolesuine,  206. 
undulations  of,  45. 
vapor  of",  .'Ji)9. 
viliuicd  by  n  crowd,  202. 
Vlbumen,  292,  291. 

effects  of,  CD  sugar,  274. 
Mcoliol,  27G. 

formed  by  fermentation  of 

sugar,  270. 
generated  by  fermentation, 
276. 

of  what  composed,  277. 
Kle  and  porter  frotii,  49. 

bc.tfle.  cork  forced  out  of,  49. 
bottled  froths,  217. 
porter  darker  tVian,  250. 
A.lkuli,  219. 

detrimental  to  combustion,  236, 
)iart.<horii  an,  219. 
Alloys,  2(>4. 

Ancients,  acquainted  with  electri- 
city, S'. 
Angle  of  incidence,  435. 

redt'ction,  4.15. 
Animal  heat.  297. 

li''e  dependent   on  vegeia- 
■)le,  305. 
Animals  good  conductors,  25. 

the  Uesh  of  olU,  tough,  293. 
Anthracite,  197. 
Antidotes  for  |>oi8on8,  324. 
Appetite,  rapid  dige.-5iion  produces, 
811. 


!  Apple,  coiitnin«  more I  ina:  i  ehcm, 
I  iiiit,4U. 

■oft  when  roHnted,  46. 
■plits  wiieii  roanted,  45. 
lApplcH,  unripe,  Sour,  318. 
I  Argund  laii.ps  do  not  «moke,  217. 
I  Allies  make  In.rd  water  soft,  I'.W 
j  Atmosphere,  327. 

polar  and  equal  r  a 
349,  350.  • 
I  Atimwpheric  air,  193,  327. 
<  Attica  and  cellars  unxufe  in  a  Bt^rm^ 
Aurora  liorealig,  367. 

cauf^c  of,  .357. 
colors  o(,  13. 
Avenue  of  trees,  445. 

i 


n. 

liaU,  hole  nuide  by,  169. 
Balls  of  fire,  why  dangerous,  20. 

run  along  the  ground,  20 
I  produce  luiM  hiff,  20. 

!  lightning  looks  like,  19. 

('        cannon,  hesited,  H>r. 
■  Balusters  damp  after  a  thaw,  405. 
Balloon,  a.^cen.sion  iji,  330. 
I  inflated,  49. 

I  lij.s.  50. 

iBaik  of  a  tree  torn  by  ligiitning,  33 
;  Barley  malted,  why,  276. 
1  how,  279 

;  not  sofTcred  to  spn  ut,  279. 

'  prevented  from  Hhooiing, 278 

Barometer,  332. 

a  weather  glass,  3.34. 
I  and  thermometer,  differ 

ence  between,  333. 
indicates  the  approach  of 

storm,  335. 
tube  of,  open,  33-1. 
u<e  of  to  sailors,  335. 
Bass  and  treble,  497. 
leasts  covered  with  fur.  etc,  88. 
IJed  a  lion -conductor,  27. 
:  Beer,  flat  if  the  ca-k  be  left  open, 

211,212,  2S1. 
I  vent  peg  be  :el.  oal,231 

ginger,  218. 
lightning  sours,  30.  37. 
vats  coniain  carboinc  acd,  208. 
yeast  converts  nutl{  into,  260. 
Bed-rooms   hospitals,  etc..  white 

washed,  516. 
Bell,  dangeious  to  ring  in  a  slo«<a 
22,23. 


INDEX. 


533 


QiU,  metal,  235,  4S7. 

sound  of  Slopped,  488. 

sounds  if  struck,  4S7. 

epiil,  makes  a  hoarse  noise,  488. 

vihrales,  467. 

wire  H  good  conductor,  24. 
UeWows  revive  m  fire,  241. 
Dells  of  trees  promote  warmth,  126. 
nest  conductors  of  heal,  79. 
Birds  keep  longer  in  their  feathers, 
290. 

3Jtck  c.oih  absorbs  heat,  149. 

dress  warm,  155. 

glass  for  spectacles,  483. 

hat  turns  red,  when,  526. 

hole  of  Calcutta,  2U3. 

kid  gloves  warm,  156,  158. 

skm  does  not  blister,  158. 

subsoil,  179. 
Blacksmiths  light  matches,  162. 
Bladder,  collapsing  of,  330. 

heat  swells  air  in  a,  43 
dlaze  tends  upwards.  234. 
Blazing  coal  burns  quickly,  231. 
Bleaching,  527. 
Block  tin,  2G2. 
Blood, 200. 

carbonic  acid  in,  298. 

chyle  converted  into,  307. 

color  of,  307. 

contains  hydrogen  and  carbon, 
297. 

food  converted  into,  306. 
oxygen  gives  vitality  to,  175, 
Blow-pipe,  186. 

hydrogen,  by  whom  in- 
vented, 137. 
Blowers  kindle  the  fire,  77 
Blue  appears  green  by  candle  light, 
480. 

Blue  fire,  how  produced,  518. 
Body,  coml)tistion  of,  299,  300 

consumes  like  a  candle,  293. 

every  part  of  warm,  297. 

fuel  of,  300. 

heat  of,  299, 

not  con.>umed,  299. 

rubbing  warms  it,  168. 

temperature  of,  123. 
Boiled  eggs  discoior  silver,  2S7. 

water  fl  it,  211. 
BliVer  of  kitchen  ranges  bursts,  why, 
59. 

B^iiAng  brine  hotter  tlian  water,  120, 
rattling  mnde  by,  117. 
walcr  bubbles,  116. 

forms  steam,  119. 


Boiling  *  «.er  heat  of,  consumed  in 
melting  ice,  133. 
in  a  fermeni,  100. 
kept  on  the  fire,  102, 
swells,  11.1. 
Books  discoiored  by  age,  522. 
Bottled  ale  froths,  217. 

pc-ter  froths,  218, 
Bottom  ot'-\  kettle  cold,  93. 

'  saucepan  covered  witb 

sooi,  IGO. 

Brass,  265 . 
Bread,  VS 

bdkiiii(  dc  ugh  converts  it  into, 
284  ■ 

becomes  iiard  by  being  kept 
128. 

full  of  holes,  285. 
leavened,  233. 
new,  indigestible,  283. 
Breath,  condensed  on  our  h-iir,  406. 

visible  in  winter,  406. 
Breathing,  how  performed,  303,  304. 

rapidly  makes  us  warjn, 
303. 

Bricklayers  cover  their  work  with 
straw,  424. 
stop  work  in  frosty  wea- 
ther, 423. 
Brewing,  yeast  used  in,  why,  280. 
Bricks  and  flag-stones  locseiied  after 
a  frost,  52. 
turn  green,  528. 
Bright  and  dark  spois  in  a  clear  fiie 
232. 

iron  in  the  fire,  178. 
metal  a  bad  radiator,  161. 
Brine  boils,  120. 

egg  floats  in  strong,  500. 
how  made,  50G. 
Britannia  metal,  2G5. 
Broth  cooled  by  blowing,  153. 

convection,  105. 
f-tirring,  105. 
Brown  paper  adhesive,  10. 

igniies    sooner  than 
white,  150. 
Bubbles  follow  the  spoon,  503. 
in  tea,  502. 

small  tend  to  the  large,  502 
Brushing  the  hair  excites  it,  11. 
Bullion,  spoons  tarnish  sooner  than, 
181. 

Burn,  ether  relieves  a,  122. 
Burnt  bread  purifies  water,  199. 
Bursting  of  ache-^inut  fhel'  iMinses  ■ 


534 


Suiter,  323. 

hard  ',n  cold  weather,  322. 

C, 

CJiikes  crisp,  523. 

Caloric,  liow  distributed,  8. 

Calcutta,  black  hole  of,  203. 

Calms,  region  of,  345. 

»"!ambric  handkerchief  feels  cool,  92. 

U indie,  body  consumes  like,  298. 

bu-ris  when  lighted,  why, 
252. 

extrnguished,  258. 
fiame  of  blown  out.  256. 

conical,  256. 

extinguished,  251. 

hand  above,  257. 

hot,  253. 

inside  hollow,  255. 
lower  part  purple, 

254. 
on  glass,  256. 
outside  yellow,  254. 
parts  of,  254. 
points  upwards,  255. 
produces  light,  254. 
yellow,  254. 
flickers,  260. 
requires  snuffing,  259. 
spirts  in  damp  weather,  302. 
tallow  of,  decomposed,  253. 
wax,  requires  no  snuffing, 

259. 
wick  of,  221. 
Cannon  balls  heated,  169. 

borers  hot,  167 
Capillary  attraction,  503. 
vessels,  297. 

combustion  in,  298. 
throughout  the  bo- 
dy,'297. 

Carbor.,  195. 

gives  firmness  to  plants,  305. 
Carbonic  acid  gas,  200. 

absorbed  by  lime, 
210. 

plants, 
207. 

accumulation  of, 
210. 

causes  death, 
201,  203,  204. 

forced  into  wa- 
ter, 216. 

formed  by  sugar, 
876. 


Carbonic  acid  gas,  geneiated  by  com 
bustion,  242. 
heavier  than  aif 
203. 

how  diffused,  207 
209. 
fatal,  300. 
found,  201. 
In  beer  vats,  206. 
in  blood,  298. 
in  the  soil,  519. 
lime  combines 

with,  212. 
of  cities  whence 

derived,  207. 
of  water,  214 
plants  absorb,  305. 
produced  by  fer- 
mentation, 210, 
276. 

renders  water  acid 
210. 

sources  of,  209. 
Carburetted  hydrogen,  220,  2-21. 

inflammable,  220 
on  marshes,  220. 
Carpenters*  tools  hot,  167. 
Carriage  in  a  tlmnder  storm,  26, 
wheels  catch  fire,  165. 
Cart  v/heels,  grease  on,  166. 
Caseine,  295. 

in  some  vegetables,  205 
Cats  and  owls  sleep  in  the  day,  432 
hair  not  smooth,  12. 
prowl  by  night  for  prey,  432. 
rub  their  ears,  11. 
wink  before  a  fire,  432. 
Cattle  good  conductors,  25. 
Cause  of  fog  and  clouds,  357. 

lightninof,  14. 
Caverns  famous  for  echoes,  500, 
Ceilings  black,  510,  511. 
Cellars  cool  in  summer,  331. 

warm  in  winter,  331. 
Chandelier,  lustres  of,  479. 
Champagne,  218. 

contains  carbonic  acid 

gas,  219. 
cork  flies  when  looaea- 
ed,  218. 
Change  of  state,  107. 
Charcoal,  196. 

fire  hot,  197. 

in  chambers,  208 
purifies  meat,  197. 
water,  199. 
Chemical  action  a  source  of  K«il  43 


INDEX. 


555 


l^emicttl  aoXioA  in  combustion,  229. 

changes  produced  by  com- 
busiion,  230. 
Chemistry,  organic,  272. 
Chextiv'it,  apples  contains  more  air 
than,  46. 
cracks  when  roasted,  44. 
oursting  of  shell,  causes  a 

report,  45. 
will  not  crack  when  slit, 
45. 

in  anney,  air  comes  down,  69, 
contracted  prevents 

smoking,  76. 
cowl  on,  73. 

will  not  prevent 
smoking,  73. 
draught  slack  in,  76. 
farm  house  smokes,  75. 
flue  high,  74. 
funnel  or  flue  of,  69. 
long,  smokes,  50. 
of  manufactories  long,  71. 
opening  of,  contracted,  72. 

too  large,  76. 
out  of  repair  smokes,  75. 
pots  increase  the  draught, 
77. 

raised  above  the  roof,  69. 

use  of,  77. 
smoke  ascends,  50,  68. 
smokes  if  it  needs  sweep- 
ing, 75. 
the  air  in  it  be 

cold,  50. 
the  flue  be  too 
short,  70. 
in  gusty  weather, 
76. 

«moky,  68. 

remedy  for,  69. 
vestry,  smokes,  73. 
wind  in  the,  51. 

strikes  against  the 
sides  of  the,  74. 
ChloriJd  of  lime,  516. 
China  cup  broken  by  hot  water,  55. 
Chlorine  gas,  antidote  for.  326. 
Choke  damp,  207. 

Church  bells,  dangerous  to  ring,  22. 

heard  at  a  distance,  489. 
congregation  drowsy,  204, 
hottest  place  in,  65. 
St.  Bride's,  destroyed  by 

lightning,  34. 
yards,  eflluvia  of.  226. 
Ohyle,  306 


Chyle  converted  into  biood,  307. 
Cider,  218. 

Cinders  lighter  than  coal,  235. 

red  hoi  sooner  than  coal,  235 

will  not  blaze,  238. 
Circle  of  fire,  460. 
Cirro-cumulus  cloudp,  372. 
Cirro-stratus  clouds,  372. 
Cirrus  clouds,  360,  370,  371 
Cities,  air  of,  impure,  2CG, 
Citric  acid,  319. 

Cleanliness,  ill-clad  averse  to,  301 
ill-fed  averse  to,  314. 
Clear  weather  ftgreeab.'e,  368. 
Close  rooms  unhealthy,  206. 
Clothes  damp  in  the  evening,  383. 
Clothing,  furs  used  for,  87. 

laborers  shouW  not  wea? 
too  thick,  130. 

loose,  warm,  89 

use  of,  88. 

warm  needed  at  night,302 
wet  with  sea  water,  130 , 
w-oolens  used  for,  87. 
Clouds,  356. 

affect  the  wind,  342. 
cirro-cumulus,  372. 
cirro-stratus.  372,  373. 
cirrus,  369,  370,  371. 
cumulo-stratus,  373. 
cumulus,  370,  371. 
division  of,  -369. 
edges  luminous,  470, 
electricity  affects,  359. 

in  the,  13. 
electrified,  of  fanciful 

shapes,  359. 
fall  in  rainy  weather,  390. 
float  in  the  air,  357. 
forests  detain  and  condense 

the,  126. 
gather  round  mountain  tops. 
374. 

general  colors  of,  360. 

not  always 
alike,  362 
height  of,  15,  358. 

lightning,  11. 
higher  on  a  fine  day,  353 
how  discharged,  14. 
in  a  negative  state  of  elec- 
tricity, 18 
positive  state  of  electn* 
city,  18. 
lighter  on  a  fine  day,  35ft 
lightning  passes  frou,  to  tk« 
earth,  13. 


530 


INDEX. 


Clouds,  moditicul ion  of,  369. 
motion  of,  362. 
nimbus^  373,  374. 
red  in  ihe  evetiitig:,  381 ,  469. 

nnori'.iiig,  331,  469. 
size  of,  35S. 
stratus,  370,  371. 
subdivision  of,  369,  372, 373. 
suddep.ly  dissipated,  353. 
thickness  of,  358. 
ihunder-bolts  never  drop 

from,  41. 
uses  of.  3G3. 
Variety  of  shape.  359. 
vary  in  form,  357. 
velocity  of,  355. 
what  are  lowest,  358. 
winds  absorb,  a59.  360. 

blow  up,  363. 

chans^e  the  shape  of, 
360. 

drive  away,  360. 
iii'jrcasc  me  bulk  of, 
360. 

UlDudy  nights  warm,  377. 
Coal,  bhck,  why,  478. 

blazing,  burns  quickly,  231. 

cinders  red  hot  sooner  than, 
235. 

lighter  than,  235 
gas,  220. 

good  for  fuel,  197. 

mines  explode,  221. 
Ooins,  silver  of  U.  S.,  264. 

gold  of  U.  S.,  264. 
Coke,  197. 

Cold,  air  condensed  by,  329. 

condenses  vapor,  134. 
blooded,  frogs  and  fishes.  301. 
car.not  penetrate  the  earth,  93. 
dead  body,  302, 
expands  water,  416. 
forests  produce,  126. 
iron  contains  heat,  162. 
long  grass  promotes,  127. 
rolling  leaves  promote,  127. 
water  on  lime,  112 
weather,  activity  agreeable  in, 
312. 

meat  and  grease  de- 
sirable Ml,  309, 

more  food  eaten  in, 
3!)9. 

when  applied  to  liquids,  102. 
Cfj>WeT  in  a  thaw  than  in  a  frost.  421. 
oi>l  of  door.s  than  in,  ft3. 


Coldness  of  the  air  increases  the  hre, 
239. 

Collapsinfrof  a  bladder,  330. 
Color,  177. 

none  in  the  dark,  480. 
Colors,  of  Aurora  Borealis,  13 
clouds,  360. 

not  always  aiike, 
G€2. 

dark  absorb  heat,  156. 
warmest,  155. 
Column  of  soldiers  marching  tc  mu- 
sic, 495. 

Combining  and  mixing,  diflerencti 

between,  35, 
Combustion,  228. 

alkaiies  detrimental  to,  230. 
capillary  ve.ssels,  298. 
chemical  action  in  2<^9. 

changes  produced 
by,  230. 
elements  of,  229, 
lermentation  prodnces,  249. 
heal  evolved  by,  228 
in  the  human  body,  299.  300 
intensity  of,  unequal,  232. 
of  fuel,  229. 

oxygen  supports,  174,  175. 
produces  light,  428. 
spontaneous,  248. 

cause  of,  248. 
sunshine  detrimental  to,  7. 
Common  solder,  266. 
Components  of  the  animal  body,  292.. 
Compression,  168. 

heat  evolved  by,  168 
Condensation,  !68. 
Condensed  air  descejids,  330. 
Conductor,  lightning  chooses  the 
best,  35. 
man  better  ihan  a  tree,  33. 
Conduction  of  heat,  79, 
Conductors,  of  heat,  good,  79,  80j  8lj 
82,  83,  84,  85 
92,  97,  98,  ^i.  ' 
cambric  92. 
fire  irons,  98. 
linen,  92. 
metals,  79,  80,  81- 

85,  97,  99. 
metal  spoon,  97. 
solid  bodies.  79, 
stone,  82,83,81 
Conductors,  oi  neat,  6ar/,  80,  82,  84. 

85,  86,  87,  88, 
90,  91,  92,  93,  <>V 
06  9€  P7  98. 


INDEX.  537 


OoaAxLttC'tL  ah.  bad,  8li,  87  89,  90, 
90,  01. 
bricks,  87,  98. 
coUon,  92. 
curtains,  124. 
down,  89. 
earth,  92,  93. 
leatliers,  89. 
far,  87. 
nair,  88 

leaves  of  trees, 
95. 

'iquids!,  86. 
oil,  96, 
paper,  95. 
porous  bodies,  80. 
snow,  94. 
soot,  96. 
straw,  90. 
water,  86. 
white  paint,  97. 
wood,  60,  82,  84. 
wool,  80,  81,  82, 
84,87,95,98. 
l>>Bductors,  oi  liglilnmg,  good,  21, 
23,  24,  25, 
28,  32. 
animals,  25. 
bell- wire,  24. 
cattle,  25. 
copper,  28. 
heated  air,  23. 
human  body, 

32. 
inside  of  a 
man,  32. 
mass  of  bodies, 

32. 
metal,  24. 
outside  of 

tree,  32. 
running  wa- 
ter, 21. 
soot,  23. 
trees,  25. 
vapor,  24. 
walls,  23. 
wet  clothes, 
28. 

Conductors,  oi  lightning,  badj  31,27. 

air,  31. 
bed,  27. 
mattrass,  27. 
Conducto:^^  lightning,  28. 

best  metal  for,  28. 
influence  of,  29,  30, 
pointed  29 


Conductors,  ightning, productive «f 
harm,  3u. 
too  small,  30. 
use  cf,  2t>. 
Conductors  of  heat  not  absorbers, 
149. 

Convection,  99. 

air  heated  by,  67. 
iron  cooled  by,  104. 
Convective  currents,  103,  328. 
Cooking,  smoke  in,  160,  161. 

vessels  with  wooden  hLTi- 
dies,  84. 
Cool  under  a  shady  tree,  91. 
Copper  and  iron  sonorous,  486. 
best  conductor,  28. 
better  than  iron,  28. 
tarnishes,  180. 
Cork  forced  out  of  ale  bottle,  49. 

of  a  champagne  bottle,  218. 
Corns  ache  before  rain,  509 
Cornea,  454. 

too  convex,  455. 
flattened,  455. 
Cornelian  transparent  when  wet, 
452. 

Corrosive  sublimate,  antidote  for, 
325. 

keeps  paste  from  souring, 
282. 

Cotton  handkerchief  feels  v/arm,  99, 
Countries  least  cloudy,  357. 

most  cloudy,  357 
Country  air  pure,  205. 
Course  of  the  wind,  342. 
Covering  radiates  heat,  131. 
Cowl,  use  of,  51. 

on  a  chimney,  73. 

not  prevent  smcke,  73c 
Cultivation  increases  warmth,  126. 
Cup,  china,  broken  by  hot  water,  55 
in  a  pie,  52. 

full  of  juice,  53. 
makes  it  boil  over,  53 
Currents,  convective,  103. 

of  air,  343,  344. 

in  a  room,  61. 
water  pass  each  other 
100. 

Curtains  bad  conductors  of  heat,121 
rooms  separated  by,  124. 

warmer  with,  91. 
sprinkled  with  water,  124 
Crov/d  unsafe  in  a  storm,  24. 
Crowded  room  produces  head-ache, 
201, 

unwholesome  209 


INDEX. 


Crystal  is  wliat,  lOo. 

Cultivated  soil  radiates  heat,  382. 

Cuinulo  stratus  clouds,  373. 

Curriuius  elouds,  370,  371. 

Cariair  juice  is  made  into  jelly,  520. 

i>. 

Ts-yi]  bci  unhealthy,  122,  '23. 
O^oduces  decay,  249. 
>  opper  sticks,  60. 
Weather,  distant  sounds  not 
heard,  4S9. 
i>^rk  colors  ahsorb  heat,  156. 

warmest,  155. 
phosphorus  luminous  in  the, 
225. 

Oavy,  Sir  Humphrey,  222. 
Dead  body  cold,  302. 

taller  than  a  living  one, 
317. 

Decanter,  stopper  of,  sticks,  59, 
Decay,  damp  produces,  249. 
of  wood,  212. 

prevented,  291. 
Decaying  vegetables,  2SS. 

mnist,  288. 
Deceptions  of  vision,  458. 
Deserts  dazzle  from  sun.«hine,  476. 
Detonating  salt  and  powder  explode, 

169. 
Dew,  374. 

abundant,  when,  376. 
and  rain,  375. 

after  a  moist  wind,  384  ,  3S5. 
cause  of  375. 

deposited  on  a  clear  night,376. 
drop  does  not  wet  cabbage, 
387. 

a  rose,  367. 

rolls,  386. 
round,  386. 

sometimes  flattened,  386. 
dry  wind  prevents,  384. 
ground  covered  with,  375. 
m  the  morning,  377. 

evening  injurious,  3S5. 
most  abundant  when,  384. 
near  walh,  378. 
none  after  a  windy  night,  379. 

on  a  cloudy  night,  377. 
some  things  covered  with,380. 
under  a  siiady  tree,  378. 
valleys  covered  with,  379. 
lainond,  195,  196. 
Oiirc-tion,  rapid,  produces  appetite, 
311 

Oi:nter  covers.  112,  143. 


Dinner  coverf  not  chased,  Xi'J. 
Discharge  of  a  cloud,  14 
Distance  makes  an  ob'ect  invisJ;!*, 
419. 

of  thu  uder  clouds  told,  40,  42. 
Distant  sounds  not  heard  in  damp 

weather,  489,  491. 
Divers  sulTer  pain  in  their  ears,  500 
eyes.  508. 
Diving  bell,  descending  in,  '330'. 
Door  and  fire  on  the  sume  side,  74. 
opposite  to  the  fire,  75. 
shrinks  in  dry  weatlier,  133. 
swells  in  rainy  weather,  133. 
Double-concave  glasses,  454. 

use  of,  455 
convex  glasses,  456. 

use  of, 

Doughjbaking  converts  it  into  bread 
284. 

effect  of  yeast  on,  283. 
fermentation  makes  it  rise, 
283 

placed  before  the  fire,  why 
285. 

will  not  rise  well  if  it  be  cold 
285. 

Down,  bad  conductor,  89. 
Draining  land,  dimini^^hes  evapora* 
lion,  126. 
promotes  warmth,  126. 
Draught,  chimney-pot  hicreases  the, 
77. 

depends  on  the  speed  ot 

smoke,  71. 
of  a  short  flue  slack,  70,  71. 
slack  in  a  chimney,  76. 
through  a  key-hole,  (i3. 

an  open  window,  64 
window  crevices  64 
under  a  door,  64. 
Draughts,  effervescing,  216. 
Dreamers  no  power  of  'UQgmeal 
.  315. 

Drum,  sound  of,  498 
Drummond  light,  187 
Dry  gla^s  filled  ah.ove  Me  Lrini^  'tC^ 
weatlier,  a  thunder-storm  .'oJ- 
/ows,  42 
soil  bard  in.  128. 
winds,  341. 

wood  burns  belter  than  green 
48,  235. 
snaps  more  than  green 
Dunghill,  heat  of,  248 
Dui^t  no  affinity  for  water,  3S1 
rfircly  flies  at  night,  37?, 


INDEX. 


539 


Diiaty  ahots  hot,  149. 
Dutch  gold,  2t>4. 

Dwelling:  parts  of,  dangerous  in  a 
stonn^  22. 

E. 

Bar-trumpets,  vise  of,  493.  , 
Earth  a  bad  conductor,  92.  i 
below  the  surface  cool  in  sum- 
mer, 93 
warm  in  winter,  93. 
colder  than  the  air,  376. 
crumbles  in  the  spring,  422. 
heal  cannot  penetrate,  93. 
rotundity  of,  451. 
warmer  than  the  air,  when, 
376. 

wet,  promotes  evaporation, 
125. 

FiUrlhenware,  271. 
Ebullition,  113. 
Echo,  499,  501,  502. 

cause  of,  499. 

caverns  famous  for,  50u. 

hali?,  etc.,  famous  for,  500, 
501. 

mountains  famous  for,  500. 
places  famous  for,  499. 
Effects  of  evaporation,  121. 

lightning,  33. 
Effervescence,  216. 

cause  of  216. 
so3n  subsides,  218. 
Effervescing  draughts,  216. 
Effluvia  of  church-yards,  226. 
Egg  fresh  or  stale,  90. 

shell  of  a  stale,  warm,  90. 
tarnishes  silver,  525. 
thick  end  cold  when  fresh,  529. 
Elbow-joint,  electric  shock  felt  at, 
30. 

Electric  shock  felt  at  the  elbow-joint, 
SO. 

Electrical  cloud, how discharged,14. 
Klectriciij  a  source  of  heat,  9. 

affects  clouds,  359. 

in  the  clouds,  13. 

invisible,  12. 

known  to  the  ancients,  9. 
negative,  18. 
odor  of,  12. 
positive,  18. 
produced  by  friction,  9. 
produces  itching,  11. 
Electrified  clouds  of  fanciful  shapes, 
35S 

Elemenlf,  non-metallic,  170. 


Elements  of  comlastion,  229. 

fuel,  229. 
Esquimaux  fond  of  train  oil,  309. 
Ether,  427. 

un{lu!ations  of,  produce  lightj 

allays  heat,  121. 

better  th-ni  water  j  121 , 
freezes  in  an  exhu'istel  t=g 

ceiver,  425. 
relieves  a  burn,  122. 
Evaporation,  121. 

carried,  on,  127. 
draining  land  diminish 

es,  126. 
effects  of,  121. 
heat  produces,  85. 
macin.tosh  prevents  123. 
of  sea,  340. 
of  water,  124. 
produces  cold,  125,425. 
reduces  lem.nerature» 
124 

wet  earth  promotes, 
125. 

'Evenmg  breeze,  352. 

clouds  red,  469. 
Ewers  break  in  a  frosiy  night,  413. 
Expansion,  43. 

of  air,  45. 
liquids  and  gases,  43. 
metals,  64. 
Explosion  of  gunpowder  produces:  j 

report,  45. 
Eyes,  do  not  see  double  with  two 
433. 

negroes  have  black,  153. 
use  of  two,  433. 
Eye  pained  by  light,  429. 

pupil  of,  dilates  in  the  dark,  423 
431. 

does  not  dilate  instantly 

430,  431. 
soon  contracts  in  the  lifk 
430,  431. 
seat  of  vision,  452. 

F. 

Fanning,  152. 

heats  the  rar,  15S 
the  face,  152. 
Farm  house  chimnt  y  smoker,  75 
Fat  persons  swim  easily,  507. 
Feathers  bad  conducior,  89. 
Feeling,  sensraion  of,  317. 

lost,  ?V 
Feet  cold  by  a  good  fir^,  ^7. 


540 


INDEX. 


Fermentation,  275. 

and  putrefaction,  275. 
compounds  produced 

by,  275. 
makes  dou^h  rise,283. 
of  sugar,  275. 
produces  carbonic 
acid,  210. 

coif;bustion,249. 

fibr.ne,  295. 

?;edle  strings  snap  in  wet  weather, 
302. 
pound  of,  498. 
f  ingcr  ?lass,  vibrations  of,  488. 
Fire,  229. 

a  little  water  makes  it  burn, 

243,  244. 
blazing,  230,  231. 
brio ht  and  dark  spots  in,  232. 
burns  bstler  in  the  open  air, 
241. 

winter  than  sum- 
mer, 239. 
briskly  in  windy  wea- 
ther, 241. 
less  fiercely  in  a  frost, 
241. 

carriage  wlieeU  catch,  165. 
cii.Mrcoal,  in  chambers,  209. 
coldness  of  air  increases,  239. 
covered,  239, 

dangerous  in  a  thunder  storm, 
23. 

door  opposite  to,  75. 

dull  if  the  flue  be  short,  70. 

revived, 245. 

stirring  quickens  a,  245. 
flame  of  a  good,  yellow,  251. 
forests  on,  167. 

goods  catch,  of  themselves, 
248. 

greasy  rags  sometimes  catch, 

250. 
heat  of,  247. 

horses  strike,  with  their  feet, 
184. 

hydrogen  gas  of,  238. 

in  adjoining  rooms  smokes,  72, 

intensity  of,  245. 

irons  good  conducl'^rs,  98. 

kindled  at  the  bottom  of  the 

grate,  234. 
light  of  237. 
neighbors  house  on,  244. 
on  a  ^rosty  night,  238. 

burns  clear,  239.  ' 
pjipei  chars  if  laid  flat  on,  242. 1 


Fire,  placed  near  the  floor,  78 

poker  laid  across  revives  it,  ?6 
powdered  sulphur  will 

quench,  245. 
produced  by  friction,  ld5 
produces  heat,  230. 
red  hoi,  230,  231. 
room  with  two,  72. 
small  opening  near  tns,  pr« 

vents  smoke,  72. 
sparks  of,  burst  from  woc<l,47. 

crackle,  47. 
stones  snap  in  the,  48. 
stronger  with  a  long  flue,  71. 
supplied  with  air,  68. 

by  a  tube,  65 
oxygen,  77. 
linder  catches,  168. 
water  extinguishes,  213. 

fuel  for,  243. 
wet  kindling  will  not  light,235 
when  does  water  extinguish, 
244. 

wood  blazes  when  near  the, 
244. 

Fish,  putrefying,  luminous,  225. 
Fishes  ascend  and  descend  in  water, 

508. 
Fixed  oils,  .321. 
Flame,  250. 

blown  inwards,  62. 

outwardSj  61. 
blueish  on  hot  cinders,  237. 
bursts  through  the  bars  of  a 

stove,  236. 
of  a  candle  blown  out,  250. 
conical,  256. 
extinguished,  251. 
hand  above,  257. 
hot,  253. 

inside  of  hollow, 
255. 

intermediate  conf 
purple,  255. 

moisture  extin- 
guishes, 48. 

on  glass,  256. 

outside  of,  yeilo-or, 
254. 

parts  of,  254. 

points  upwards,  255 

produces  light,  254 
a  good  fire  yellow,  251. 
gas,  258. 

greenish  yellow,  237. 
will  not  pass  through  wiro 
gauze,  222. 


INDEX. 


541 


Flame,  yellow,  bright.  251. 
Flannel  keeps  us  warm,  301. 
Flash,  the  sound  of  thunder  foUowa 

the,  41. 
Flbit-irons  hot,  135. 
F'esh  of  old  animals  tough,  293. 
Flint  struck  against  steel,  163. 
riowers  amell  sweeter  before  rain, 

134. 

f  .B8  of  a  ehiivr.ey,  69. 

stoves  should  be  blackened, 
140. 

Fluidity,  mercury  distinguished  by 

its,  54. 
Flutes,  498. 
Fog,  406. 

and  clouds,  cause  of,  357. 

difference  between, 
356. 

Fogs  common  in  valleys,  411. 

do  not  occur  every  night,  408. 
occur  at  night  when,  408. 
over  rivers  and  marshes,  408. 
sun  red  in,  470. 
wind  dissipates,  411. 
Food,  306. 

converted  into  blood,  306. 
more  eaten  in  cold  weather, 
309. 

F  lot- warmers,  covered  with  flan- 
nel, 98. 
polished  thi,  98. 
marks  covered  with  ice,  414, 
415. 

Forests  detain  and  condense  clouds, 
126. 
on  fire,  187. 

prevent  the  access  of  wind 

and  smi,  126. 
produce  cold,  126. 
Forked  lightning,  15. 
France  and  Germany  warmer  than 

formerly,  127. 
Fresh  water  sparkles,  214. 
Friction,  165. 

disturbs  latent  heat,  166. 
fire  produced  by,  165. 
produces  electricity,  9. 
Progs  and  fishes  cold-blooded,  301. 
Frost,  bricks  loosened  after,  52. 

makes  the  earth  crack,  432. 
on  tomb-stones,  157. 
work  on  wmdows,  402. 
Froth  and  spray  white,  478. 
of  ale  and  porter,  49. 
fermented  liquors,  281, 
Frozen  dew  411. 

46 


Fruits  and  vegeta  bles  c»Ojin|f,  310^ 
311. 

fall  from  the  tree,  502. 
more  eaten  in  hot  weather. 
310. 

Fuel,  coal  good  for,  197. 
combustion  of,  229 
elements  of,  229. 
of  the  body,  306. 
stones  unsuitable  for  j98 
Fulgurites,  33. 
Funnel  of  a  chimney,  69. 
Fur,  beasts  covered  with,  88. 

prevents  heat  from  escapnig,88. 
used  for  clothing,  87. 
pMrnaces  built  of  bricks^  98. 

doors  covered  with  clay 
and  sand,  99. 
Furniture  of  a  room  of  the  same  teni' 
perature,  83. 

G. 

Gallery  the  hottest  part  of  the  build- 
ing, «5. 
of  a  church  hotter  than  the 
aisle,  66. 
Galvanized  iron,  265. 
Gas,  327. 

and  liquids,  514. 
carbonic  acid,  200 
carburetted  hydrogen,  220,  221 
coal,  220. 
elasticity  of,  515. 
flame,  258. 
hydrogen, 184. 
nitrogen,  192. 
oxygen,  170. 
Gases,  expansion  of,  43. 

from  putrefying  substances,  991 
Gaseous  substances,  108. 
Gelatine,  295. 
German  silver,  264. 

tarnishes,  181. 
Ghost  stories,  how  originated,  99i. 
Gideon's  miracle,  383. 
Ginger  beer,  218. 

pop,  217. 
Glass,  266. 

a  good  radiator,  403. 

reflector,  476. 
a  reflector  of  light,  444. 
breathing  on,  dulls  it,  404. 
broken  by  hot  water,  55. 
of  a  window  cool,  401,  409. 

cold  water  misty,  403. 
opaque  when  ground,  472. 
outside  of,  not  expaiided,  M 


512 


INDEX. 


GlMS;  plate,  267. 

ground,  267. 
for  what  used,  267. 
porcelain,  earthenware,  266. 
enaps  when  unequally  ex- 
panded, 55. 
worked,  286. 
OljiMSS,  double  concave,  454. 

use  of,  455. 
convex, 456. 

use  of,  456. 
suited  for  old  persons,  456. 
Glazier,  mending  a  window,  10. 
(jriazing,  270. 
Globular  lightning,  16. 
Gloves,  black  kid,  warm,  156,  158. 
Lisle  thread  cool,  156,  157. 
w^hite,  158. 
Glow-worms  glisten  by  night,  432. 
Glue  adhesive,  129. 
Gluten,  278. 

changed  by  putrefaction,  3^7. 
Gold,  182,  1S3. 

coins  of  U.  States,  264. 
Dutch,  264. 
jewellers',  264. 
Goods  catch  fire  of  themselves,  248. 
Grape«juice,  yeast  not  needful  in,278. 

sugar,  274. 
Grapes  on  the  vine,  278. 
Graphite,  195. 
Glass  a  good  radiator,  381. 

long,  promotes  cold,  127. 
wood,  etc  ,  radiate  heat,  380. 
Grate,  fire  kindle/l  at  the  bottom  of, 
234. 
red  hot,  101. 
Gravel  a  bad  radiator,  381. 
Gray  morning  indicates  a  fine  day, 
386. 

Grease  on  cart  wheels,  166. 

prevents  rust,  177. 

soap  destroys,  3-23. 

turpentine  extracts,  321. 
O'asasy  paper,  unfit  to  wriie  on,  321. 

rags  sometimes  catch  fire,  250. 
SfreftTi  fire,  how  produced,  517. 

gooseberries  hard,  520. 

tea  unwholesome,  326. 
wood  snaps  little,  48. 
Grotesque  figures  in  hot  coals,  232. 
Ground  cold  on  a  clear  night,  376. 

glass  opaque,  472. 

hoar-frost,  411. 

hardened  by  the  sun,  129. 
Guano  as  a  manure,  519. 
Gum  adhesive,  129. 


Gunpowder,  211. 

explosion  r»f,  iS. 
Gusty  weather,  chimneys  sinck6  ir 
76. 

Gutta  percha,  324. 

H. 

Hail,  398. 

attended  with  thunder,  398. 
falls  generally  in  summer,  3»lf 
two  things  essential  to 
cause,  399. 
Hair,  brushing  excites  it,  11. 
Halls  famous  for  echoes,  500. 
Hams  smoked,  526. 
Halo  round  the  moon,  367. 
Handle  of  a  metal  pot  made  of 

wood,  85. 
Hands  chap  m  frosty  weather,  341. 
Hard  and  soft  soap,  difference  be- 
tween, 322. 
Hard  water  agreeable  to  drink,  214. 

exposed  to  the  air,  214. 
made  soft  by  ashes,  190. 
unsuitable  for  washing, 
188. 

Harm,  lightning  conductors  pp^duC" 

tive  of,  30. 
Hartshorn,  an  alkali,  219. 
Hawks  see  at  a  distance,  457. 

within  half  an  inch  of 
the  eye,  457. 
Hay-stacks  catch  fircj  249,  250. 
Haze  round  the  sun  indicates  rain, 
367. 

Head-ache  produced  by  a  crowded 

room,  201. 
Health  injured,  123. 

open  air  best  for,  205. 
Hearing,  boundaries  of  human,  496 
Hearth-rug  a  non-cojiducior,  8-i. 
stone  feels  hot,  83. 

cold,  83. 
the  temperature  of  the  car* 
pet,  83. 

Heat,  7. 

air  absorbs,  15r'. 

draws  away  from  us,  8ft, 

expanded  by,  43. 

never  radiates,  385. 
all  bodies  contain,  111. 
applied  to  the  bottom  of  th( 

kettle,  lUl. 
bad  radiator  of,  130. 
best  conductors  of,  79, 
cainiol  penetrate  the  earsh,  9S 
causes  per  pi  ration,  S'Ja, 


INDEX. 


543 


Heal,  che.nical  action  a  source  of  ,43. 
conduction  of,  79. 
conductors  of,  79. 
covering  radiates,  131. 
curtains,  bad  conductors  of, 
124. 

decomposes  wood,  137. 
dies  not  always  produce  light, 
250 

effect  of,  on  the  air,  332. 
electrieii /  a  source  of,  9. 
evolved  by  combustion,  228. 

compression,  168. 
ftipwds  air,  332. 

substances,  43,  44. 
furs  prevent  from  escaping, 
88. 

in  cold  water,  112. 
ice,  110. 

proved, 111. 
latent,  110,  162. 

aisturbed  by  friction,  166. 
liberated,  253. 
made  sensible,  164. 
liquids  impart  no  extra,  120. 
melts  metals,  136. 
mercury  expands  by,  54. 
metal  expands  by,  56. 
of  a  dunghill,  248. 
a  large  man,  249. 
ice  made  sensible,  426 
our  bodies,  298,  299. 
boiling  water  consumed  in 

melting  ice,  136. 
the  sun,  7. 
ozygen,  the  cause  of  animal, 

paint  blisters  from,  131. 
polished  metal  a  conductor  of, 
146. 

p.?incipal  source  of,  7. 
produced  by  fire,  230^  247. 

mechanical  ac- 
tion, 161. 
produces  evaporation,  86. 
radiated  by  every  thing,  139. 
radiation  of,  137. 
reflection  of,  144. 
reflectors  of,  145. 

polished  metal, 
145. 

seeks  an  equilibrium,  83- 
sensation  of,  produced,  8. 
separates  water,  115. 
softens  wax,  136. 
awells  air  ir  a  bladder,  4.3. 
#arps  wood,  524. 


Heat,  water  a  bad  ccnduclor  of,  86^ 
proved, 
101. 

whence  derived,  112. 
wood  a  bad  conductor  of,  80. 
woolens  prevent  from 

escaping,  88. 
worst  conductors  of,  80. 
Fledges  pr()ni{)ie  warmth,  126. 
Height  of  clouds,  15,  358. 

lightning  clouds,  14. 
mountains  measured,  334 
Hills  appear  larger  in  wet  weather, 
4U9. 

farther  off  in  wet  wea- 
ther, 409. 
and  mountains  change  the 
wind,  339. 
Hoar-frost,  411. 

covers  ground  and  trees, 
412. 

from  frozen  fog,  4 12. 
none  under  shady  trees, 
412. 

on  grass  and  vegetables. 
413. 

only  after  a  clear  nighti 
412. 

Hole  made  by  a  ball,  169. 

Honey-dew,  385. 

anis  fond  of,  386. 
effect  of,  on  leaves,  386 

Hoops,  heated  red  hot,  56. 

Horn  transparent,  452 

Horses  snuff  up  air  before  rain,  134 
strike  fire  with  their  feet,  164 

Hospitals,  contagious  matter  re- 
moved, 5i5. 

Hot  air,  houses  heated  with^  51, 
bricks  heat  the  feet,  87.' 
broth  cooled,  105. 
cannon  borers,  167. 
carpenters'  tools,  167. 
cinders,  flame  blueish  on,  237 
cloudy  nights  oppressive,  368 
coals,  grotesque  figures  in,  23''4 
fire  red,  230. 
food,  blowing  cools,  106. 

frate,  red,  101. 
oops  heated  red,  56 
how  to  keep  water,  102. 
iron,  176. 

bends  easily,  108. 
cooled  by  rad.ation,  140 
converts  water  inlu 
steam,  132. 

why,  133 


544 


INDEX. 


H*tlroa,  diop  ef  water  rolls 
over,  134 . 


kettle  holder  does  not  feel,  95. 

lid  of  kettle,  96. 

metal  feels  warmer  than  hot 

wool,  80. 
mush  keeps,  103. 
particles  of,  water  ascend,  101. 
poker  handle,  78. 
room  quickly  cooled,  65. 
rotting  leaves,  215. 
eilver  spoon,  97. 
soup  keeps,  102. 
starch  keeps  v/ater,  103. 
tea  cooled  by  stirring,  105. 
tire  heated  red,  57. 
water  breaks  glass,  55. 

china  cup  broken  by,  55. 
melts  sugar,  191. 
razor  di})ped  in,  56. 
soon  freezes,  108. 
weather  followed  by  thunder 
storms,  42. 
fruits  relished  in,  310. 
produces  laziness,  308. 
Hottest  place  in  a  church,  65. 
House  heated  with  hot  air,  57. 
m  a  valley  stnokes,  73. 
lightning  knocks  down,  34. 
part  of,  safest  in  a  storm,  26. 
Houses  in  a  street,  44G. 

seem  smaller  in  the 
distance,  447. 
Human  body  a  good  conductor,  32. 
Hunger,  311. 

cold  produces,  311. 

felt  less  in  the  night  than  in 

the  day,  312. 
produces  laziness,  314. 
produced  by  singing,  314. 
reading  aloud  creates,  312. 
work  produce?,  312,  313. 
Hydiogen,  184. 

and  water,  184. 
carburetted,  220.  221. 

on  marshes,  22<^, 
inflammable,220. 
characteristics  of,  185. 
combustible,  185. 
destroys  life,  185. 
discovered,  when,  1S5. 
gas  of  fire,  238. 
has  no  taste,  185. 
phosphuretted,  226. 
uses  of,  186. 


i. 

Ice,  413, 

contains  latent  heat,  lft7. 
foot  marks  covered  with,  4U, 
415. 

heat  in,  110,  111. 

of  made  sensible,  426. 
houses  lined  with  straw,  96. 
lighter  than  water,  413. 
melted  by  the  sun,  136. 
on  a  river,  417. 
rubbed  together  melts,  166. 
salt  dissolves,  421. 
Bulphuric  acid,  etc.,  dissolve*; 
422. 

Ignis  fatuus,  226. 

flies  from  us,  227. 

follows  us,  228. 

ignited,  227. 
Ill-clad  averse  to  cleanliness,  301. 
lU-fed  averse  to  cleanliness,  314. 
Incidence,  line  of,  434. 
Indian-rubber  erases  pencil  marks 
517. 

makes  paper  adhesive,  9. 
Inflated  balloon  rises,  50. 
Influence  of  lightning  conductors, 
29,  30. 

Inhabitants  of  warm  countries  live 

on  fruits,  310. 
Injur}^  from  ligiitning,  to  avoid,  27. 
Ink-spot  black,  475. 

turns  yellow,  475. 
Inner  pot  cannot  boil,  119. 
Insects  fly  low  in  wet  weather,  394. 

walk  on  the  ceiling,  512. 
Insensible  perspiration,  401,  403. 
Intensity  of  combustion  unequal^ 
232. 

fire  depends  on  what,  245. 
Inverted  ship,  459. 
Invisible  vapor,  118. 
Iris,  453. 

Iron  a  bad  absorber,  150. 

afl!"ected  by  lightning,  38. 
air  rusts,  176. 

better  conductor  than  woodj  8X 
bright,  on  the  fire,  178. 
cinders  will  not  burn,  198. 
cold,  contains  heat,  162. 
contracts  on  cooling,  56. 
drop  of  water  rolls  over  hct| 

134,  135. 
flat,  hot,  135. 
galvanized,  2€5. 
handle  not  colder    than  .)i9 
pump,  81. 


INDEX. 


54o 


Uoa  hot,  1 76. 

bciids  easily,  108. 
converts  water  into  steam, 

132,  133. 
ma(1e  r-;d,  by  hammering, 

K)2. 

pump  handle  feels  cold,  81. 
ruais,  176,  521. 

in  damp  air,  177, 179. 
6t»jel  made  from,  263. 
vvire,  a  gon]  c(;rductor  of 
sound^  494. 
jiJaitd?,  lemperamre  of,  150,  151. 
trh,52l. 

itching  produced  by  electricity,  11. 
J. 

Jjick-o'Laniern,  2*26. 
JeweIIer*s  gold,  264. 
Fungles,  204. 

K. 

Kettle  boils  over,  116. 

bottom  of,  cold,  96. 
bri-ht,  148. 

covered  with  soot,  155 
does  not  sing  114. 
heat  applied  to  the  bottom  of, 
101. 

holder  does  not  feel  hot,  95 

woolen,  95. 

paper,  95. 
lid  of,  hot,  96. 
new  155. 

sings  on  the  side  of  the  fire, 
115. 

most,  when,  114. 
when  cooling,  115. 
spout,  water  runs  out  of,  117. 
Rey-hole,  draught  through,  63. 

L. 

Lar^tic  acid,  319. 

fiakes  rarely  freeze,  420. 

springs  pre  »ent,  freezing,  421. 
[,amp-black,  196. 

glass  diminishes  the  smoke, 

247. 
safety  221,  222. 
Eraokes.  why,  240. 

when  the  wick  is  un- 
even, 240. 

high, 246. 

Isind  breeze  cool,  354. 

unhealtliy.  .353. 
(^planders  wear  fur  550. 
L«te  spring,  521 

4t>* 


Latent  hear,  110,  182. 

developed  from  woc<t« 
165. 

disturbed  by  friction, 

166. 
in  water,  111. 
liberated,  253. 
made  sensible,  164. 
not  perceptible,  111. 
Laudanum,  antidote  for,  325. 
Laziness  produced  by  hnl  weather, 
308. 


x-<cau,  vviiiir.,  4,uo. 

not  sonorous,  436. 
oxidizes,  ISO. 
Leather,  318, 

moist,  attached  to  a  stone, 
511. 

Leaves,  brown  in  autumn,  479. 

effect  of  rain  on  fallen,  393. 
green,  479. 

rough,  radiate  heat,  330 
Lid  of  a  kettle  hot,  96. 

saucepan  bright,  159. 
tight  on  a  boiler,  116. 
Life,  animal,  dependent  on  vegeta* 
ble,  305. 
oxygen  sustains,  175. 
vegetable  dependent  on  animal, 
306. 
Light,  427. 

absorption  of,  429. 

all,  travels  equally  fast,  428. 

combustion  produces,  428. 

Drummond,  187. 

eye  pained  by,  429. 

from  houses,' trees,  etc.,  428. 

heat  not  always  productive  of, 

250. 
of  a  fire,  237. 

oxygen  refracts  very  little,  173 
reflection  of,  429. 
thrown  off  in  rays,  429. 
travels  rapidly,  427. 
undulations  of  ether  produce, 
427. 
Lightning,  13. 

affects  iron  and  steel,  33. 
air  a  non-conductor  of,3 1  * 
resists  the  passage  of, 

bark  of  a  tree  torn  by,  33. 
cause  of,  14. 
chooses  best  condactds, 
35. 

clotid.  discharged,  21. 


546 


INDEX. 


Usktmng,  clouds,  height  of,  14. 

common  in  summer  and 

autumn,  17. 
conductors,  28. 

best  metal  for,  28. 
influence  of,  29,30. 
pointed,  29. 
productive  of 

harm,  30. 
too  small,  30. 
use  of,  29. 
destroys  life,  19. 

when,  19. 
does  not  sour  old  beer,  37. 
effects  of,  33. 
flash  straight,  15. 
followed  by  wind,  16. 

rain,  16. 

forked,  15. 

f lobular,  16. 
nocks  down  houses,  34. 
looks  like  balls  of  fire,  19. 
magnetic  needle  reversed 

by,  38. 
metal  fused  by,  37. 
oaks  often  struck  by,  31. 
parts  the  air,  31. 
passes  from  the  clouds  to 
the  earth,  18. 

earth  to 
the  clouds,  18. 
|)ersons  maimed  by,  19. 
produces  fulgurites,  33. 
proceeds  from  a  positive 

body,  18. 
purifies  the  air,  37. 
runs  down  the  inside  of  a 

man,  32. 
sheet,  16. 

fit.  Bride's  church  de- 
stroyed by,  34. 
summer,  17. 

to  avoid  injury  from,  27. 
trees  broken  by,  30. 

conductoTs  of,  25. 

scorched  by,  17. 
turns  beer  sour  36. 

milk  sour  35. 
two  flashes  of  forked,  15. 
Sig-zag,  15. 

inductors,  good,  32,  28. 

25,24  23,21, 
metals,  24. 
mass  of  bo- 
dies, 32. 
human  body, 


Lightning  conduct or«,  goody  mth,6% 
of  a  tree,  32 
inside  of  a 

man,  32. 
copper,  28. 
wet  clothes, 

28. 
trees,  25. 
animals,  25. 
cattle,  25. 
vapor,  24. 
bell-wire,  24 
walls,  23. 
heated  air. 23 
soot,  23. 
running  wa* 

ter,  21 
bad,  31,  27. 
air,  31. 
bed,  27. 
mattress,  27. 
use  of,  29. 
best  metal 

for,  28. 

Lilac  steel,  178. 

free  from  rust,  179. 
Lime  and  water  combine,  36. 
cold  water  on,  112. 
combines  with  carbonic  acid, 
212. 

decomposes  offensive  gases, 
516. 

marl,  etc.,  as  manure,  519. 
phosphate  of,  224. 
quick,  absorbs  carbonic  acid 
210. 

Limes  and  Lemons  sour,  318. 
Lme  of  incidence,  434. 

reflection,  435. 
Linen  dried  by  the  wind,  125. 

in  the  air,  125. 
shirt  colder  than  cotton,  91. 
water  cleans,  189. 
wind  dries  damp,  350. 
Liquefaction,  135. 
Liquids  bad  conductors  of  heat,  06 
99. 
boil,'ll3. 

changed  to  steam,  109. 

expansion  of,  43. 

impart  no  extra  heat.  120. 

not  elastic,  515. 
Liquid  substances,  108. 
Liquors,  froth  of  fermented,  281. 

gurgle  when  decanted^  510 
Loaf  sugar,  274. 

Localities,  thunder  nffected  by  40 


INDEX. 


547 


Lo;idon  fog,  iflS, 
Long  wick  bent,  259. 
Loose  clothing  v/arm,  89. 
Lucifer  matches,  130,  224. 

ignite,  225. 

M. 

Masintosh  prevents  evaporation j  123. 
Magnetic  needle  reversed  by  light- 
ning, 38. 
Maiic  acid,  318. 
M'ilt.  278. 

Ma",  belter  conductor  than  a  tree,  33. 

may  discharge  a  cloud,  22. 

on  the  top  of  a  spire,  447. 

shrinks  when  starved,  314. 
Manufactories,  chimneys  of,  long,71. 
Manure  makes  land  fertile,  518. 
Marking  ink,  527. 
Marsupium,  457. 

Mass  of  bodies  good  conductor,  32. 
Matches,  blacksmiths  light  their,  162. 
lucifer,  130,224. 

ignite,  225. 
Mattress  a  non-conductor,  27. 
Meat  and  grease  desirable  in  cold 
weather,  309. 
disliked  in  hot 
weather,  310. 
putrefies  in  hot  weather,  228. 

changeable  wea- 
ther, 289. 
salted  less  nutritious  than 

fresh,  293. 
salt  preserves,  294. 
taint  of,  removed,  289,  317. 
taints  on  a  moonlight  night, 

143. 
tough,  293. 
Mechanical  action,  161. 

heat  produced 
by,  161. 

Melted  wax,  hard  when  cold,  107. 
Mercury  distinguished  by  its  fluidi- 
ty, 54. 
expands  by  heat,  54. 
rises  in  the  thermometer,  55. 
MVal,  bell,  265. 

Britannia,  265. 
expansion  of,  54,  56. 
fused  by  lightning,  37. 
handle  burns  the  hand,  85. 

hotter  than  a  wooden 
one,  85. 
hot,  feels  warmer  than  hot 

wool,  80. 
naeked  by  heat,  136. 


Metah  moot  raric  conductor  of  heat, 
79. 

polished,  a  bad  radiator,  142. 

conductor,  146. 

reflecloi,116y  147. 
will  not  coLect  dew,'38J, 
383. 

pot,  handle  of,  made  of  wood, 
84. 

spoon  a  conductor  of  neat,97 
tea-pot  of  polished,  141,  H2 
Metals,  262. 

and  alloys,  262. 
combine  with  oxygei.,  180, 
Meteorology,  327. 
Middle  story  safest  in  a  storm,  26. 

why,  27 

Milk  boils  sooner  than  water,  107. 
over,  113. 
easily  burns,  292. 
lightning  sours,  35. 
rennet  curdles, 319, 
sour,  curdles,  319. 
stale,  curdles  when  boiled,  282- 
turns  sour,  281. 

in  hot  weather,  282 
Miner  lowers  a  candle,  201. 
Mineral  springs,  188. 
Miners  in  danger,  222,  223. 
Mines,  coal,  explode,  221. 

ventilation  of,  60. 
Mirrors,  268. 

rays  of  light  reflected  by,  434 
reflect  our  image,  434,436. 
small,  reflect  our  whole  per 
son,  437. 
Miscellaneous,  502. 
Mist,  399. 

and  dew  vanish  at  sun-rise,  407. 
fog,  375. 

difl"erence  between,  4 11, 
not  dew,  406,  407. 
windows  covered  with,  400,402 
Modification  of  clouds,  369. 
Moisture  extinguishes  flame,  48. 

dissolves  salt,  130. 
Money  in  our  pocket  feels  hot  before 

a  fire,  80. 
Monsoons,  346. 

change  of,  marked,  how,  348, 
limits  of,  346. 

more  powerful  than  trade 
winds,  347. 
useful  than  the  trad« 
winds,  348. 
Moon  appears  large  in  the  horizoo* 
443. 


548 


INDEX. 


Wooii  appears  larj^er  than  the  stars, 
448. 

like  a  flat  surface,  449. 
halo  round,  3C7. 
light  oil  water,  441. 
shadow  of,  475. 
Moraing  breeze,  352. 

clouds  red,  469. 
M  rtar,  '213. 

adhesive,  213. 
becomes  hard,  213. 
crumt)les  in  frost,  423. 
^oics  of  dust  in  the  air,  106. 
Mother  of  pearl,  471. 
Moulding,  269. 
Mouldy  bread,  529, 
Mountain  top,  difficult  to  breathe 

on,  332. 
Mountains  affect  thunder,  40. 

free  from  noise,  403. 
height  of,  measured,  334. 
Mountainous  countries  rainy,  391. 
Motion  of  the  sea,  341. 
Motions  real  and  apparent,  345. 
Mush  keeps  hot,  103. 
Musical  glasses,  498. 
sounds,  496. 

and  noises,  496. 
Mutton  fat  solid,  321. 

N. 

Nail  beaten  by  a  hammer,  163. 
Near-siglitedness,  cause  of,  453,457. 

glasses  for,  454. 
Negative  electricity,  18. 
Negroes,  157. 

have  black  eyes,  158. 
Neighbor's  house  on  fire,  244. 
Nimbus  clouds,  373,  374. 
r  ■•♦.ric  acid  purifies  the  air,  38. 
*~  'rogen,  192. 

'  and  air,  192. 

oxygen  mix,  36. 
colorless,  193. 
does  not  sustain  combus- 
tion, 193. 
expired,  202,  303. 
when  discovered,  192. 
Non-rnetallic  elements,  170. 
Nof^i,  where  the  sun  is  vertical, 
337. 

North  winds  generally  cold,  351. 

dry,  351. 

O. 

Oaks  oftpa  £'/T'.k  by  lightning,  31. 


Oar  in  water  bent,  462, 
Objects  cannot  be  counted  wkcn 

riding  rapidly,  458. 
Ocean  affecis  the  wind,  340. 
Odor  of  electricity,  12. 

air  filled  v.'ith,  before  rain,  133 
134. 

Oenanthic  acid,  318. 
Oil,  198. 

liquid,  321. 

prevents  water  freezing,  % 

salad,  323. 

thick  in  winter,  322. 
Oiled  paper  transparent,  472, 
Oils,  320. 

fixed,  321. 

volatile,  321. 
Old  people  far-sighted,  457. 

unable  to  walk,  505. 

saucepan  boils  soon,  159. 
Oleine,  321. 

Opening  of  the  chimney  contracted^ 
72. 

Optics,  427. 

Orange,  accidental  color  of,  482. 
Organic  chemistry,  272. 
Oxalic  acid,  antidote  for,  326. 

removes  ink  spots,  527. 

Oxides,  175. 
Oxygen,  170. 

and  carbon  unite  in  the  blood 
300. 

nitrogen  mix,  36. 
oxides,  170. 

difference  be- 
tween, 170. 
by  v/hom  discovered,  171. 
cause  of  animal  heat,  175. 
fire  supplied  with,  77. 
gives  vitality  to  the  blood,  175 
in  the  blood  produces  heat,303 
its  use,  172^  175. 
less  in  damp  weather,  173. 
metals  combine  with,  180. 
more  in  clear  frosty  weather, 
173. 

never  liquid  or  solid,  172. 
no  taste  or  smell,  172. 
of  plants,  305. 

refracts  light  very  little,  172. 
supports  combusti(m,  174, 175. 
sustains  life,  175. 
tinder  supplied  with ,  103, 164 
want  of,  relaxes  the  eystera. 

173, 174 
who  gave  i'  Ike  C'lrie,  171. 
Ozone,  li?. 


mbEX. 


549 


p. 

fkiiX  I  listers  from  heat,  131 
preserves  wood,  97. 
prevents  rust,  177. 
apei  a  bad  conductor,  95. 

adhesive  when  rubbed,  10. 
burns  more  readily  than  wood, 
233. 

chars  if  laid  flat  on  a  fire,  242. 

curls  when  scraped,  524. 

extinguisher,  258. 

greasy  unfit  to  write  on,  321. 

kettle  holder,  95. 

puckers  when  wetted,  392. 

wood  burns  longer  than,  234. 
Parlor  smells  of  soot  in  summer,  77. 
Partial  vacuum,  62. 
Pa'tiiion  walls,  492. 
Paste  adhesive,  129. 

corrosive  sublimate  prevents 
turning  sour,  282 
Pearl  divers  ofien  deaf,  508. 
Percussion,  161. 

Persons  who  live  in  close  rooms 
pale,  308. 
open  air  »-ud- 
dy,  308. 

Perspective,  450. 

Perspiration,  insensible,  401,  403. 

produced  by  heat,  302. 
Petrefactions,  189. 
Petrels,  394. 
Pewter,  265. 
Phosphate  of  lime,  224. 
Phosphorus,  223. 

and  phosphuretted  hy- 
drogen, 223. 

discovery  of,  224. 

how  obtained,  223. 

inflammable,  224. 

luminous  in  the  dark, 
225. 

Phosphuretted  hydrogen,  226. 
Piano  fortes,  sound  of,  498. 
Picture  reflects  light  when  varnish- 
ed, 474 
Pie,  cup  in,  52. 

full  of  juice,  53. 
makes  it  boil  over,  53. 
Places  most  dangerous  in  a  thunder- 

stirm,  20. 
Plai!  tB  absorb  carbonic  acid,  305 
bend  towards  the  glass,  525. 
carbon  gives  firmness  to,  305. 
grow  OH  moonlight  nights,143. 
out  of  walls,  518. 


Plants,  oxygen  of,  .305. 

some,  close  their  leaves  before 

rain,  513. 
white,  when  kept  in  the  dark, 

481. 

Plaster  round  a  stove  cracks,  58. 

why,  .58,  59 

Plate  glass,  267. 

for  what  used^  267. 
ground,  267. 
warmers,  145,  146. 
Platinum,  182. 

used  for  crucibles,  183. 

celicate  instro- 
ments,  182. 

Plumbago,  178. 

Pointed  lightning  conductors,  29. 

Poisons,  antidotes  for,  32-1. 

Poker  feels  colder  than  the  rug,  81. 
handle  hot,  78. 
laid  acro!=s  a  fire  revives  it,  78 
red-hot,  how  carried,  79. 

Polar  currents,  344. 

Pond,  sides  of,  covered  with  leaves, 
503. 

Poor,  averse  to  ventilation,  300. 
Pop-gun  makes  a  report,  510, 
Porcelain,  268. 

how  long  baked,  269. 
of  what  composed,  268. 
Pores  of  wood,  47. 
Porous  wood  snaps,  47. 
Porter  darker  than  ale,  280. 
Positive  body,  li^-htiiing  proceeds 
from,  1§. 
electricity,  18. 
Pot  of  water  in  a  saucepan,  119. 
Potassium,  183. 

and  water,  184. 
Potatoes  cooked,  how,  106. 

exposed  to  the  air,  green, 
484. 

Primrose  is  yellow,  why,  478. 
Proof  spirit,  277. 

Proportions  of  the  air  not  desti  eyed, 
304. 

Prussic  acid,  antidote  for,  324. 
Pump  handle,  iron,  feels  inten.iefy 
cold,  81. 
water  hard,  187,  188. 
Pupil  of  the  eye,  453. 

contracted,  4i?3. 
Putrefaction,  286. 

compounds  produced  ly 
286. 

dilference  between,  atMl 
fermentation,  286. 


550 


INDEX. 


i^trefaction  produces  carbonic  acid, 
210. 

Putrefying  body  offensive,  226,  287. 
fish  luminous,  225. 
substances,   gases  from, 
227. 

Putty,  loose  pieces  of,  electrified, 10. 
Q. 

Quadrupeds  swim  easily,  506. 
Q,aick-lime  absorbs  carbonic  acid, 
210. 

how  produced,  213. 
R. 

Radiation,  137. 

depends  on  roughness, 138. 
hot  iron  cooled  by,  140 
of  fuel,  138. 
Radiator  of  heat,  139. 

bright  metal,  bad 
141,  161. 
glass  a  good,  403. 
Rail-way  train  over  a  bridge,  495. 
Rain,  338. 

a  passing  cloud  often  drops, 
389. 

air  filled  v/ith  odor  before, 

133,  134 
cools  the  air,  125. 
does  not  always  fall  at  night, 

389. 

drops  sometimes  very  large, 
390. 

effect  of,  on  fallen  leaves,393, 
falls  in  drops,  389. 

most  when,  388. 
haze  round  the  sun  indicates, 
367. 

horsessnuff  up  air  before,  134. 
less  in  summer  than  winter, 

lightning  followed  by,  16. 
more  falls  by  night  than  day, 
393. 

in  winter  than  summer, 
393. 

purifies  the  air,  391. 
snow  and  hail,  388. 
swallows  fly  low  before,  393. 
water  fertilizing,  388,  390. 

not  salt,  191. 

smells  badly,  190. 

soft,  189. 
wind  increases  the  size  of  i 
drops,  390.  I 
ftaiiabow,  cause  of,  465. 


Rainbow,  two  al  one  timt  406 
colors  reversed,  <i67. 

Rainy  days,  most  when,  388. 

Rarefied  air  ascends,  66. 

a  bad  conductor  of  scuu4 
490. 

nourishes  fire  iesp  lhan 
cold,  240. 
Rarefaction  of  air,  66. 
Rarity  of  air  diminishes  sound,  491, 
Rats  and  mice,  remedy  for,  526. 
Rattling  made  by  boiling,  117. 
Ray  of  light  bent,  461. 

composed   of  various 

colors,  477. 
divided,  4G4. 

by  a  prism,4^ 
refraction  of,  465. 
Razor  dipped  in  hot  water,  56. 
Reading  aloud  creates  hunger,  312. 
Red,  accidental  color  of,  4?1. 
fire,  how  produced,  51'";, 
hot  poker,  how  carried,  79 
wick  kindled,  252. 
Reflection,  473. 

from  mirror,  474 
of  heat,  144. 

light,  429,  473. 
line  of,  435. 
Reflectors  of  heal,  145. 

not  absorbers,  145 
of  polished  metal, 

145,  146. 
should  be  bi  [ght,  117. 
tin,  keep  the  kitchen  cool, 
147. 

Refraction,  461. 

Refrangible  rays,  361. 

Region  of  calms,  345. 

Remedy  for  a  smoky  chinuicj ,  ®3v. 

Rennet  curdles  milk,  319. 

Retina  of  the  eye,  452. 

Returning  stroke,  17. 

Rising  sun  in  summer  causes 

breeze,  352. 
River  appears  shallow,  463. 

bottom  of,  never  frozeTi,  418. 

ice  of,  of  unequal  thidbiesa* 
419. 
on,  417. 

not  frozen  solid,  418. 

sides  of,  192 . 

vegetation  on  margin  of,  50-4. 
water  freezes  at  the  surfacf 

of,  first,  418 
of  feels  warm  in  win 

ter,  419. 


INDEX. 


551 


Roai^ted  appl  »  ?\i\'A,  45. 

made  soft,  46. 
chestnuts  crack,  44. 
Rocks  bad  radiators,  382. 

often  split  in  winter,  414. 
Rjllinpf  thunder,  cause  of,  41. 
R  jora,  close,  unhealthy,  206. 

lict,  quickly  cooled,  65. 
separated  by  curtains,  124. 
jgpriiikling  a  hot,  cools  it,  124. 
vapor  of,  401,  404. 
void  of  air  in,  supplied,  63. 
warmed  by  a  stove,  87. 
warmer  than  the  open  air,  63 
with  curtains,  91. 
double  doors,  91. 
with  two  fires,  72. 
Rose  is  red,  why,  477. 
Rotation  of  the  earth,  336. 

affects  the  air, 
337. 

Rotting  leaves  hot,  215. 

promote  cold,  127. 
Rotundity  of  the  earth,  451. 
Rubbing  the  body  warms  it,  166. 
Running  makes  us  warm,  302. 
water,  191. 

a  good  conductor,  21. 

freezes  slowly,  4 18. 

ice  of,  rough,  419. 

pure,  290. 
Rush  light  extinguished,  257. 

by  a  pin,  260. 

Rust,  175. 

grease  prevents,  177. 
iron,  176. 

paint  prevents,  177. 
S. 

Safest  place  in  a  storm,  25. 

way  to  travel  in  a  thunder 
storm,  26. 
Batety  lamp,  221,  222. 
Sailors  wet  with  sea-water,  123. 
§alad  oil,  323. 

3al-aEratu3  makes  cakes  light,  212. 
Sail  and  snow  colder  than  snow, 
422,  425. 
beef  produces  scurvy,  296. 
blackens  silver,  181. 

how  removed, 
181. 

crackles,  137. 
dissolves  ice,  421. 
moisture  of  air  dissolves,  130. 
preserves  r^eat,  294. 
wmter,  18S 


Salted  meat  less  nutritious  than  freshj 
293. 

Sands  of  diffeitnt  colors  mix,  35. 

do  not  com- 
bine, 36. 

Saucepan,  bottom  of,  covered  wit« 
soot,  160. 
lid  bright,  155. 
old,  boils  soon,  159. 
Savages  plan  to  detect  the  nppTfea<:? 

of  an  enemy,  486. 
Scurvy,  lime  juice  a  cure  for,  599. 

produced  by  salt  beef,  298. 
vegetables  a  remedy  for,296t 
Sea  breeze  cause  of,  353. 
cool,  354. 
healthy,  353. 
in  tropical  islands,  35? 
evaporation  of,  340. 
gulls,  394. 

heaves  before  a  storm,  491. 
luminous.  226. 
motion  of,  3U. 
water  brackish,  191. 

clothes  wet  with,  130. 
easy  to  swim  in,  505. 
rarely  frozen,  420. 
waves,  354. 
Sensation  of  heat  produced,  8. 
Shadow  of  the  moon,  475. 

size  of,  445. 
Shallow  water  soon  freezes,  419. 
Shavings  non-conductor  of  sound, 
492. 

Shear  steel,  263. 

Shell  of  a  stale  egg  warm,  90. 

Sheet  lightning,  16. 

tin,  262. 
Sheets  damp,  123. 
Ship  in  the  air,  459. 
inverted,  459. 

seen  below  the  horizon,  470 

Shock,  electric  felt  at  the  elbow 

joint,  30. 
Shoes,  dusty,  hot,  149. 
Shrubs  liable  to  be  frost-bitten,  Hi 
Shutter,  unsafe  to  bar,  in  a  storm,  21. 
Sick  persons  eat  dry  toast,  198. 

why,  199. 

room  kept  free  from  effluria, 
515. 

Sides  of  a  river,  192. 

Silver  coins  of  United  S  aJes.  264. 

German,  264. 

salt  blackens,  181. 

how  removed  J 191 

spoon  hot,  97. 


552 


INDEX. 


Silver  tarnishes,  180. 

by  egg, 525. 
Simmering,  what,  114. 
Singing  produces  hunger,  314. 
Sir  Humphrey  Davy,  221. 
Size  of  clouds,  358. 
Sky  blue,  why,  480. 

covered  with  clouds,  474. 
3'9ii*»p,  315. 

no  will  in,  316. 
prevents  our  seeing,  315. 

feeling,  316. 
hearing,  316. 
tasting,  316. 

BiecT  395. 
Smoke,  67,231. 

and  steam  curl,  68. 
as'^ends  a  chimney,  60,  68. 
faiis  before  rain,  134. 
HI  cooking,  160, 161. 
lamp  glass  lessens  the,  247. 
little,  with  a  red  hot  fire,  232. 
more  when  fuel  is  added,  231. 
of  a  candle,  260. 
prevented,  how,  72. 
why  do  lamps,  246. 

not  Argand  lamps, 
247. 

Smoky  chimneys,  68. 

remedy  for,  69. 
Smooth  surfaces  reflect  light  best, 
476. 
transmit  sound 
486. 

Smouldering  wick  rekindled,  251. 
Snow,  395. 

a  bad  conductor  of  heat,  94, 
396. 

and  sugar  white,  479. 
cause  of,  395. 
falls  in  winter,  395. 
keeps  the  eartli  warm,  396. 
like  wool,  94,  396. 
melts  near  a  wall,  140. 
none  in  summer,  397. 
nourishes  the  earth,  397. 
salt  and  snow  colder  than, 
422. 

aome  mountains  covered 

with,  397. 
use  of,  395. 
warm,  397. 
white,  398. 
*oap,  189,  320. 

bubbles,  color  of,  468. 

thickness  of,  469. 
destroys  grease,  323. 


Soap  destroys  pai«t,  320. 
Soapy  waler  lathers,  321. 
Soda  water,  217,218. 
Sodium,  183. 

and  wnter,  184. 
Soft  water  suitable  for  v/ashint  190 
Soil  hard  in  dry  weather,  128. 
Solder,  common,  266. 
Soldiers,  column  of,  marching  to  ina 

sic,  495. 
Solid  substances,  108. 
Some  things  colder  than  olhsrs,  '''9. 
Sonorous  bodies,  485. 
Soot,  kettle  covered  with,  155. 

parlor  smells  of  in  summe 77 
Sorrel  removes  ink  spot-,  527. 
Souchong  tea  poisons  flies,  326. 
Sound,  485. 

heard  better  by  night  than 
day,  492. 
in  clear  wea- 
ther, 489. 
through  wa- 
ter, 494. 
loud  in  caves, 

493. 
near  the  poles, 

490. 
not  distinct  in 
hot  weather 
490. 
produced, 

how,  485. 
travels  at 
what  rate, 
485. 

Sour  milk  curdles,  319. 

South  winds  generally  warm,  351. 

Soup  keeps  hot,  102. 

Sparks  of  fire  burst  from  wood,  47. 

crackle,  47. 
Spectacles,  black  glass  for,  483. 
Spirit,  above  and  below  proof,  277. 
proof,  277. 

what  wines  contain  the  mort, 
277. 

Sponge,  516. 

wet,  cleans  a  slate,  517 
swells,  391. 
Spontaneous  combustion,  248. 

cause  of, 
248. 

Spoon  in  water  bent,  462. 

tarnishes  sooner  than  bulli«)n,  181 
Spring  water  cool  in  summer,  94. 

sparkles,  211. 
Springs  prevent  lakes  freezing,  421 


553 


gprmkling  a  hot  room  cools  it,  124. 
Biagnant  water  full  of  worms,  290. 

putrefies,  290. 
Stale  boiled  eggs  offensive,  287. 
3tirch  adhesive,  129. 

glazes  linen,  523. 

keepjt  water  hot,  103. 

Btillens  linen.  523. 
r'^n  moon  seems  larger  than,  448. 

more  visible  from  a  mountain, 
442. 

not  visible  in  the  day-time, 
433. 

reflection  of,  in  a  well,  440. 
seen  from  the  bottom  of  a  well 

in  the  day,  433. 
twinkle;  471,  473. 
Blarvation,  effects  of,  315. 

produces  madness,  315. 
States,  many  of  them,  warmer,  125. 
Steam  burns  severely,  210. 
condensed,  109,  118. 
dispersed,  118. 
engines  burst,  110. 
invisible,  1C9,  IIS. 

from  kettle  spout, 
109 

liquids  converted  into,  1OO.,1O0 
Stearine,  321. 

Steel  affected  by  lightning,  38. 

flint  struck  against,  163. 

hard  and  brittle,  262. 

lilac.  178. 

free  from  rust,  179 

made  from  iron,  263. 

shear,  263. 
Stethoscope,  493. 

Stone  hearth  feels  colder  than  tfte 
carpet,  82. 
a  good  ccmductor  of 
heat,  82. 
snaps  m  the  fire,  43. 
unsuitable  for  fuel,  198. 
Stoneware,  270. 

glazed,  how,  270. 
Stopper  of  a  decanter  sticks,  59. 

smelling  bottle  sticks,  60. 
SCCrmj  attics  and  cellars  un.safeiu  a 
thunder,  23. 
carriage  in  ;i  thunder,  26. 
density  of  air  previous  to,  331. 
fire  dangerous  in  a  thunder,  23 
middle  storv  sat'est  in  a  thun- 
der, 20,  27, 
^pression  fd  '  previous  10^331 
pari  of  a  hr^       ^fest  in  a 
Shundcr,  26 


Storm,  part  of  a  house  d  a:igerou8  is  e 
thund  er,  22. 
places  (langerodf  in  a  thuo 

der,  20. 
safest  place  in  a  thunder,  25. 
to  be  wet  in  a  thunder, 
28. 

way  to  travel  in  a  thun- 
der, 26. 
theatre  unsafe  in  a  thunder,  24. 
thunder,  follows  dry  weather, 
42. 

preceded  by  hot  wea- 
ther, 42. 
rarely  follows  wet 
weather,  42. 
tinsafe  to  bar  a  shutter  in  a 
thunder,  24. 
be  in  a  crowd  in, 
24. 

lean  against  a  wall 

in,  23. 
ring  bells  in,  22, 

23. 

run  or  drive  fast  in 
22. 

vapor  increases  the  danger  in, 
24. 

Stove,  blackened,  178, 

crackles  with  a  hot  fire,  57. 

when  cooling,  58. 
flue  connected  with  should  be 

black,  140. 
plaster  round  cracks,  58,  59, 
room  warmed  by,  87. 
rusty,  177. 
should  be  iron,  99. 

placed  near  the  flucr 
67. 

Stratus  cloud?,  370,  371. 
Straw,  bricklayers  cover  their  wo>:  k 
with,  424. 
delicate  trees  covered  with, 
424. 

ice  houses  lined  with,  96. 
in  a  barrel  of  liquor,  511. 
water  pipes  covered  with,  421 
Street,  hou.ses  in,  446. 

seenr\ smaller  m  the 
distance,  447. 
Striking  iron  makes  it  red  hot,  192. 
Strings  flat  when  unstrung,  4^ 
Stucco  peels  in  frosty  weather,  423 
Substances,  all,  radiate  heat,  1S^. 
are  gaseous,  108. 
liquid,  109, 
Kolid, 


554 


INDEX. 


SubslaiMJcs  which  ladiate  heat  ab- 
sorb it,  139. 
Bwddcn  change  of  temperature,  352 
8ugar,  272 

and  salt  retard  boiling,'  1 19. 

a  vegetable  substance,  272. 

ferrnentfition  of,  275. 

flavors  water,  190. 

forms  alef)bo!,  276, 

carboi'ic  acid,  276. 

from  the  suijar  cane,  273. 

grape,  274,  275. 

how  obtained,  273. 
refined.  273. 

loaf,  274. 

long  in  melting,  503. 
lump  of,  in  tea,  512. 
Sulphur,   powdered,  will  Qiiench 

fire.  245. 
Bulphuric  acid  and  water,  112. 
Summer  lightning,  17. 
Sun  and  m'>on,  magnitude  of,  458. 

stars  appear  flat  surfaces, 
449. 

appears  Inrge  in  the  horizon,443. 
does  not  heat  the  air,  328. 
fades  artificial  coh)rs,  481 
ground  hardened  by,  128. 
heat  of,  7. 
ice  melted  by,  136. 
red  in  a  fog,  470. 
rise  gray  or  red,  366. 
red,  365. 

indicates  rain,  385. 
light  on  water,  441. 
reflection  of,  in  a  well,  439. 
set  coppery  yellow,  364. 
gray  indicates  rain,  366. 
red,  363. 

indication  of  a  fine  day, 
364. 

yellow  indicates  rain,  3G5. 
btinshine  detrimental  to  combustion, 
7,  2-40. 

Surfaces,  some  brilliant  others  dull, 
428. 

Swallows  fly  low  before  rain,  393. 

Swans  and  ducks  dive,  387. 

Sweet- wort,  eft'ect  of  yeast  upon,  280. 

T. 

Taint  of  meat  removed,  289,  29Q, 

317. 
Tallow,  198. 

of  a  candle  decomposed,  253. 
Tamarinds  sour,  319. 
Tannic  acid,  318. 


Tartaric  acid,  3! 9. 

Taste,  power  of  ,  317 

Tea,  green,  unwholesome,  326. 

Tea,  hot,  cooled  by  stirring,  105 

faster  in  a  ?aucci 
129. 

pot  of  black  earthen,  141,141 

polished  metfil,  14  1. 
S(mchniig  poisons  flies,  326. 
Telescopes,  451. 

use  of,  150. 
Temperature  of  IsUmds,  150,  151, 
the  body.,  84,  123. 
reduced   by  evapora 
tion,  124. 
Thaumatrope,  46!). 
Theatre  utisafe  in  a  storm^  24. 
Thermometer,  333. 

mercury  rises  in,  M 
Thickness  of  clouds.  358. 
Thunder  a  deep  growl.  40. 

an  irregular  roar,  39. 
bolts  never  drop  from  th<i 

clouds.  41. 
cause  of  roiling,  41. 
cloud,  a  man  may  discharge 
22. 

distance  of  clouds  told,  40 
42. 

mountains  affect,  40. 
one  vast  crash,  39. 
sound  of,  affected  bv  local: 
lies.  40. 

follows  the 
flash,  41. 
storm,  attics  and  cellars  uu 

safe  in.  23. 
carri.ige  in,  26. 
crowd  un.'^afe  in,  24. 
fire  dangerous  in.  23. 
follows  dry  weather,  42. 

wot  weather  rare- 
ly, 42. 

middle  story  safest  in,  26, 
27. 

part  of  a  house  safest  in,  26. 

dangerous 
in'.  22. 
places  dangerous  in,  20. 
preceded  by  hot  weather,4-2. 
Thunder  htorm,  safest  place  in,  25. 

way  to  travel 

in,  26. 
to  be  wet  in, 
28. 

theatre  unsafe  in,  2i. 
to  bar  a  shutter  un- 
safe in,  24. 


INDEX. 


55b 


rhandor  storm,  to  lean  acraiust  a 
wall  uMHafe  in,  23. 
unsafe  to  ring  bells 
in,  2-2.  23. 
run  or  drive 
fast  ill,  22. 
vapor  increases  the 
dai'fiter  in,  24. 
Tigers  see  in  the  dark,  431 

prowl  hv  niirlit  for  prey,  432. 
fimb^rs  charrt^d,  iDd. 
Tin,  blofk.  262 

foot  warmers  covered  with 
rtaiuiel,  98. 
polished,  98,140. 

reflector,  147. 
sheet,  262. 
Tinder  catches  fire,  168. 

su[)plied  with  oxygen,  163, 
164. 

Tire  heate  d  red  hot,  57. 

shrinks  on  cooling.  57. 
Tomb-slones,  frfist  on,  l.")?. 
Top  of  walkinor-sticks,  523. 
Tough  meat,  293. 

llie  flesli  of  old  animals,  293. 
Trade  winds,  342,  3-13,  345,  346. 

of  'he  Indian  Ocean, 
347. 

why  so  called,  342. 
Train  oil,  E»~uiinaux  fond  of,  309. 
Transmission  o.' sound,  485. 
Transparency,  cause  of,  472. 
Tree,  bark  of,  lorn  by  lightning,  33. 

broken  by  lij?htning,  30. 

conductor  of  lightning,  25. 

ligntning  runs  down,  31. 

man  a  better  conductor  than, 
33. 

scorched  by  lisfhtning,  17. 
Trees,  avenue  of,  445. 

seem  to  approach 
in  the  distance,  446. 
covered  with  straw,  424. 
render  the  air  wholesome, 
206. 

Tropical  islands,  sea  breeze  in,  352. 

subject  to  a  land 
breeze,  354. 
l^rpentine  extracts  grease,  321. 
1  wilight,  470. 

U. 

(Uidulations  of  th.e  air,  45. 
Unseasoned  wood  soon  decays,  291 . 
(Jnjskillful  swimmers  sink,  506. 
Use  of  chimney-pot»,  77. 


1  Use  of  clothing,  88. 

1  ligliiiiing  coiK  uctOTg,  2f, 

1  Uses  of  oxygen,  175. 


Vacuum  filled,  62. 

pariia',  62. 
Valley,  hou<e  in,  smoke?,  7S. 

C(wered  with  dew,  379. 
Vapor,  400. 

a  conductor,  24. 

cold  air  condenses,  134. 

cojuieiised,    refracts  yejcif 

rays,  361. 
invisible,  119. 
of  a  room,  401,  404. 
the  ai.',  399. 

sea  not  salt,  129. 
removed  by  evaporation,  125. 
unconde.ised,  refracts  red 
rays,  304. 
Vaporization,  131. 

and  evaporatif)n,  dif 
ference,  132. 
Varnished  pictare  reflects  light,474 
i  Vegetable  life  dependent  on  animal, 
306. 

[  Velocity  of  clouds,  355. 

wind,  355. 
I  Vent  peg  of  a  beer  ca^k,  509. 
i  Ventilation,  60, 

of  a  room,  65. 

mines,  (  6. 
poor  averse  to,  300. 
Verdigris,  antidote  for,  3'i(6. 
Vertical  rays,  337. 
Vessels,  capillury,  297. 

combustion  in,  2^ 
throughout  ihe 
b(tdy,  2'.^7. 
Vestry  chira'  evs  smoke,  73. 
Vibrations   aecessary   to  prv>duc« 
sound,  497. 
number  of  appreciated , 
497. 

which  soonest  heard;  33, 
Vinegar  sour,  320. 
Violet,  accidental  color  cf,  483. 

is  l)lue.  why,  477. 
Vision,  how  pioiluced,  453. 

the  eye  the  seal  of,  452. 
Void  of  air  in  a  room  supplied,  63. 
Volatile  oils,  321. 

W. 

Walls  of  a  house  damp  in  a  lhafv, 
404  ,  4')d. 


556 


mDEX 


Willis  aria  tfe  to  lean  agJisiis^t  in  a 

stor  ji,  23. 
Wariu,  breavhing  rapif^.y  makes  us, 
302. 

fiannf  j  keeps  ub,  M'i 
running  makes  us,  '^^^2. 
Warmer  in  u  frost  than  sn  a  thaw, 
421, 

Warmth,  belt^  of  trees  promote,  126. 

cuhivaiion  ircreases,  126. 
draining  of  land  promotes, 
126. 

hedges  promote,  l'2fi 
of  man}-  of  th  e  Stales,  125. 
Water,  187. 

a  bad  conductor,  88,  lOi. 

a  better  conductor  than  air, 
85. 

aerated,  217. 

a  ilitle,  makes  a  fire  burn, 

243^  214. 
and  Bir  rot  wof-d,  528 
potassium,  1P4. 
lime  combine,  36. 
sulphuric  aci(!,  112. 
wine  casks  charred,  199. 
boiled,  flat,  211. 
boilmgj  bubbles,  116. 

heal  of  consumed, 136. 
in  a  ferment,  100. 
kept  on  the  fire,  102. 
swells,  115 
bottle  of,  wetted  with  ether, 
424. 

burnt  bread  purifies,  199. 
carbonic  acid  of,  214. 

forced  into,  2i6 
renders, 
acid,  210. 

cleans  linen,  13  . 
clothes  wet  wi.  i  sea,  123, 
13;J. 

con\rerted  into  steam,  102, 
131. 

currents  of,  100. 
curtsuu?  sprinkled  with,  124. 
depih  of,   ret-'iTUs  freezing, 
4-20. 

drop  of,  rolls  over  hot  iron, 

13i,  1.35. 
etht;r  allays  hf:at  better  than, 

12t. 

expanded,  117. 
es'jands  froin  rolri.  416. 

he:.C,  415. 
extinguishes  I.  fire,  243,  244. 


Water,  fluid,  187. 

freezes  first  at  tiic  surface  ot 
rivers,  416. 
sooner  when  exposed. 
131. 

than  mi)k.fl2e 
fresh,  sparkles.  '214. 
fuel  for  fire,  243. 
hard,  agreeable  to  drir-ic,  5 \i 
exposed  to  the  air,  2U 
made  soft  by  ashes,  IDO 
unsuitable  for  washing 
188. 

heat  separates,  115. 
hot,  breaks  glass,  55. 

china  cup  broken  by,  55. 
iron  converts,  into  steam. 

132,  133. 
melts  sugar,  191. 
soon  freezes,  108, 
how  heated,  100. 
hydrogen  and,  184 
image  in,  inverted,  437,438* 
rain,  not  salt,  191. 

smells  badly,  190. 
soft,  189. 
razor  dipped  in  hot,  56. 
running,  191. 

pure,  290. 
runs  out  of  the  kettle  spcut, 

117. 
salt,  188. 

sea,  brackish,  191. 

latent  heat  in.  111. 

less  subtile  than  air,  86. 

melts  salt,  504. 
sugar,  504 . 

milk  boils  sooner  than,  107. 

not  so  hot  as  land,  ^0. 

of  a  river  feels  warm  in  win 
ter,  419. 

oil  prevents  freezing,  96. 

particles  of  hot,  ascends,  101, 

pipes  burst  in  frosty  wea- 
ther, 415. 

ponds  of,  evaporated,  127. 

pot  of,  in  a  saucepan,  119. 

produces  a  sensation  of  co 
85. 

pump,  hard,  187,  188 
shallow,  soon  freezes,  419. 
spilled  on  a  table  cloth,  505 
simmers,  1 13. 
soapy,  lathers,  321. 
soda.  217,  218. 
sodium  and,  184. 
soft  suitable  for  washing,  19ft. 


INDEX  > 


557 


Water,  spring,  cool  in  summer,  94. 

sparkles,  211. 
slagiianl  pu'refies,  290. 

full  of  worms,  290. 
Watering  the  streets  cools  Ihem,  124. 
WaXj  198. 

melted,  hard  when  cold,  107. 
softened  by  heat,  136. 
Waxing  thread  strengthens  it,  522. 
Wsst  wir.ds  in  Atlantic  Stales  gene- 
rally dry,  350. 
fiel  clothea  conduct  lightning,  28. 
give  us  cold,  122. 
in  a  thunder  storm,  28. 
earth  promotes  evaporation, 124. 
feel  cold,  122. 
finger  feels  cold,  121. 
kindling  will  not  light  a  fire, 

235. 
summer,  125. 
weather  oppressive,  368. 

rarely  precedes  thun- 
der storms. 
wheels,  128. 
Wheels  constantly  wet.  ^■23. 
White,  accidental  color  of,  483. 
dress  cool,  148. 
fire,  how  produced,  518. 
lead,  263. 

of  egg  clarifies  coffee,  528. 
skin  blisters,  158. 
Wick,  candle,  221. 

long  bent,  259. 
red  hot  kindled,  252. 
smouldering,  rekindled,  251. 
Will-o'-the-wisp,  226. 

flies  from  us,  227. 

Wini,  336. 

accelerates  evaporation,  125. 
against  the  sides  of  a  chim- 
ney, 74. 
always  in  motion,  336. 
cause  of,  336. 

changes  of,  affect  clouds,  357. 

eloud-.5  affect  the,  342. 

cold,  154. 

course  of,  342. 

dissipates  fog,  411. 

does  not  always  blow  one 

way,  339. 
dries  damp  linen,  350. 
expansion  of  air,  causes,  349. 
forests  prevent  the  access  of, 

196 

fcnerally  cold,  355, 
ills  and  mountains  affect,339. 
in  the  chimney,  51. 

47* 


Wind,  lightning  followod  by,  .9. 

linen  dried  by,  125. 

oc<"an  affects  the,  340. 

sometimes  brings  rain,  353. 

velocity  of,  355. 
Winds  absorb  clouds,  359,  360. 

blow  regularly.  3-12. 
up  cloud. ^,  3&3. 

chansre  the  shape  of  cL  ad», 
360. 

drive  away  clouds,  383. 
dry,  341. 

increase  the  bulk  of  clo«  la, 
360. 

north,  generally  cold,  351. 

dry,  351, 
south,  ofenerally  warm,  351. 
west,  m  Atlantic  states  dry. 
350. 

which  blow  over  water  rainy, 
351. 

Windy  weather  c  )ld,  90. 
Wind-mill,  sails  /  /,  512. 
Window  blazes  at  sun-set,  438. 
glazipr  mending,  10. 
rattling  of,  486. 
reflects  noon-day  sun,  438, 
Wine  ca'ks,  old,  offensive,  318. 
stain  removed,  522. 
turns  sour,  why,  320. 
Wire  gauze,  flame  will  not  pf&a 

through,  222. 
Wisdom  of  God  manifested,  91,  93, 

128.  348,  380,  382,  417,  422. 
Wooa.  bad  conductor  of  heat,  60. 
blazes  when  very  near  the 

fire,  244. 
burns  longer  than  paper,  234. 
decay  of,  212. 

prevented,  291. 
decomposed  by  heat,  137. 
dry  burns  better  than  green, 
48,  235. 
snaps  more  than  green,  48* 
green  snaps  little,  48. 
latent  heat  developed  from, 
165. 

paint  preserves,  97. 

paper  burns  more  readily  than 

233. 
pores  of  47. 
porous  snaps,  47. 
seasoned,  how,  291. 
sparV^  of  fire  burst  from,  47. 
two   )ieces  burn  better  thai 

oi  v  ,  238. 


558 


INDEX. 


A  ool,  fur  bet  ween  ihe  ^bres  of,  89. 

war  Hi.  31>«. 
Woolen  OH rp^^t  n  bad  conducior  of 
hr;it. 
kenle  holder,  95. 
preve  Us  heal  from  e.«cap- 

used  for  clothing,  87. 
Work  produces  hunger,  312,  313. 
f^GTit  5»f*fiflac!org  of  heat,  80 


Y. 

Yeast,  279. 

Converts  m?»It  into  beer.  280. 
effecis  of  upon  dou<;h,2^^3. 

fe wee t  won, 280 
in  prnpe  juice,  not  needftt' 
278. 

used  in  brewin?,  w^Tf  260 
Yellow  flame  bright,  251. 

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